INTERROGATED TRANSPONDER SYSTEM

• US 3,757,035 A
• Filed: 04/21/1970
• Issued: 09/04/1973
• Est. Priority Date: 04/21/1970
• Status: Expired due to Term

• Current Assignee: Herbert W. Sullivan
• Original Assignee: Herbert W. Sullivan
• Inventors: Sullivan, Herbert W.
• Primary Examiner(s): Britton, Howard W.
• Application Number:
  US05/030,599
• Time in Patent Office: 1,232 Days
• Field of Search: 178/5.1,DIG.13 340/408,152,150 179/2A,2AS 325/31,308
• US Class Current: 725/107
• CPC Class Codes: G08B 26/00 Alarm systems in which substations are interrogated in succession by a central station
• CPC Class Codes: G08B 26/003 replying the identity and the state of the sensor
• CPC Class Codes: H04H 60/21 Billing for the use of broadcast information or broadcast-related information
• CPC Class Codes: H04H 60/32 Arrangements for monitoring conditions of receiving stations, e.g. malfunction or breakdown of receiving stations
• CPC Class Codes: H04H 60/43 for identifying broadcast channels
• CPC Class Codes: H04H 60/96 CATV systems for accessing the Internet H04H60/86
• CPC Class Codes: H04N 2007/17372 the upstream transmission being initiated or timed by a signal from upstream of the user terminal
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04Q 9/12 using combinations of frequencies

Abstract

A system, method and apparatus for selectively interrogating transponders which are located at remote stations connected to a central interrogating station. In one embodiment, a number of transponders which make up a final group within a larger group of transponders, all attached to a common line running from the central station, are selected and simultaneously caused to retransmit modified interrogation signals in accordance with certain informational characteristics and the identity of each transponder retransmitting. The final group of transponders chosen to be interrogated is selected by first sending a number n of tones of a larger group of tones m down a branch line to partially activate some of the transponders. These tones are followed by a smaller number of tones k chosen from the group n to which only the transponders in the final group respond. The system is particularly designed for use in a subscriber television network and specific circuitry for accomplishing the logical and electrical functions required are described.

Claims

1. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said preDetermined number are integers, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the central station for transmitting a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, where k is less than n, and a number of interrogation signals;

means at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the respective associated receiving means and means at each transponder responsive to said actuating signal for transmitting the modified interrogation signals to the central station.

2. A subscriber television system as set forth in claim 1 wherein each transponder in each final group has means for imparting a predetermined identifying characteristic to the modified interrogation signals retransmitted to the central station.

3. A subscriber television system as set forth in claim 2 wherein the interrogation signals produced and transmitted by the central station are data bit pulses having two levels, and the means at each transponder in each final group for imparting the identifying characteristic to the modified retransmitted interrogation signals comprises circuit means operative to produce tone pulses of a characteristic frequency in response to modified data bit pulse interrogation signals of one of said two levels.

4. A subscriber television system as set forth in claim 2 wherein the interrogation signals produced and transmitted by the central station are data bit pulses having two levels, and the means at each transponder in each final group for imparting the identifying characteristic to the modified retransmitted interrogation signals comprises oscillator means for producing a tone signal, and means responsive to one level of the modified data bit pulse interrogation signals of one of said two levels for gating the tone signal of the oscillator means for retransmission to the central station.

5. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said predetermined number are integers, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the central station for transmitting a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, meAns at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the respective associated receiving means, means at each transponder responsive to said actuating signal for transmitting the modified interrogation signals to the central station, means at each transponder in a final group for imparting a predetermined identifying characteristic to the modified interrogation signals retransmitted to the central station, means at the central station responsive to the said predetermined identifying characteristic for separating the received retransmitted signals, and means at the central station for obtaining information from the retransmitted modified interrogation signals after separation as to the condition and tuning of the receiving means of the subscriber station associated with the transponder in the final group retransmitting the modified interrogation signals.

6. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said predetermined number are integers, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the central station for producing and transmitting to the transponders of said plurality of stations:

a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals chosen from said first set of n signals, where k is less than n;

a number of interrogation signals; and

a plurality of respectively different identifying signals, the number of these identifying signals being equal to the predetermined number of subscriber stations in a final group, means at each transponder of a respective final group responsive to the reception of predetermined first and second sets of n and k signals for producing a transponder actuating signal, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the respectively associated receiving means, means at each transponder of a final group for selecting one of the plurality of different identifying signals, means at each transponder for varying a characteristic of the selected identifying signal in accordance with the modified interrogation signals, and means at each transponder responsive to the transponder actuating signal for retransmitting the selected identifying signal with modified characteristic to the central station.

7. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said predetermined number are integerS, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the transponders of each major group responsive to a predetermined first set of n selection signals and means at the transponders of each final group within a major group responsive to a predetermined second set of k selection signals transmitted from the central station for producing a transponder actuating signal, means at the central station for producing and transmitting to said plurality of transponders predetermined first sets of n selection signals and predetermined second sets of k selection signals to cause the production of said transponder actuating signal at the transponders of selected final groups within each major group operating on said single circuit, means at the central station for transmitting a number of interrogation signals to said plurality of transponders, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the receiving means associated with the respective transponder, and means at each transponder responsive to the production of said actuating signal for retransmitting the modified interrogation signals to the central station.

8. A subscriber television system as set forth in claim 7 wherein each transponder in each final group has means for imparting a predetermined identifying signal to the modified interrogation signals retransmitted to the central station.

9. A subscriber television system as set forth in claim 8 wherein the interrogation signals produced and transmitted by the central station are data bit pulses having two levels, and the means at each transponder in each final group for imparting the identifying characteristic to the modified retransmitted interrogation signals comprises circuit means operative to produce tone pulses of a characteristic frequency in response to modified data bit pulse interrogation signals of one of said two levels.

10. A subscriber television system as set forth in claim 8 wherein the interrogation signals produced and transmitted by the central station are data bit pulses having two levels, and the means at each transponder in each final group for imparting the identifying characteristic to the modified retransmitted interrogation signals comprises oscillator means for producing a tone signal, and means responsive to one level of the modified data bit pulse interrogation signals of one of said two levels for gating the tone signal of the oscillator means for retransmission to the central station.

11. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said predetermined number are integers, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the transponders of each major group responsive to a predetermined first set of n selection signals and means at the transponders of each final group within a major group responsive to a predetermined second set of k selection signals transmitted from the central station for producing a transponder actuating signal, means at the central station for producing and transmitting to said plurality of transponders predetermined first sets of n selection signals and predetermined second sets of k selection signals to cause the production of said transponder actuating signal at the transponders of selected final groups within each major group operating on said single circuit, means at the central station for transmitting a number of interrogation signals to said plurality of transponders, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the receiving means associated with the respective transponder, means at each transponder responsive to the production of said actuating signal for retransmitting the modified interrogation signals to the central station, means at each transponder in a final group for imparting a predetermined identifying characteristic to the modified interrogation signals retransmitted to the central station, means at the central station responsive to the said predetermined identifying characteristic for separating the received retransmitted signals, and means at the central station for obtaining information from the retransmitted modified interrogation signals after separation as to the condition and tuning of the receiving means of the subscriber station associated with the transponder in the final group retransmitting the modified interrogation signals.

12. A subscriber television system comprising a central station having means for transmitting television signals and other information signals over a single operating circuit to a plurality of subscriber stations up to a number equal to the product of m things taken n at a time, times n things taken k at a time, times a predetermined number of subscriber stations in each final group operating on the single circuit, where m, n, k and said predetermined number are integers, each subscriber station having means for receiving the television signals and displaying the video portion thereof and for receiving the other information signals and a transponder to be selectively interrogated as part of a said final group of transponders to produce information upon interrogation of the condition and tuning of the respective receiver associated with a transponder, there being a number of major groups of subscriber stations operating on said single circuit and at least one final group within each major group, means at the transponders of each major group responsive to a predetermined first set of n selection signals and means at the transponders of each final group within a major group responsive to a predetermined second set of k selection signals transmitted from the central station for producing a transponder actuating signal, means at the central station for producing and transmitting to said plurality of transponders predetermined first sets of n selection signals and predetermined second sets of k selection signals to cause the production of said transponder actuating signal at the transponders of selected final groups within each major group operating on said single circuit, means at the central station for transmitting a number of interrogation signals to said plurality of transponders and a plurality of different identifying signals of a number equal to the predetermined number of subscriber stations in a final group, means at each transponder for modifying the received interrogation signals in accordance with the condition and tuning of the receiving means associated with the respective transponder, means at each traNsponder of each final group for selecting a different one of the plurality of different identifying signals, means at each transponder for varying a characteristic of the selected identifying signal in accordance with the modified interrogation signals, and means at each transponder responsive to the transponder actuating signal for retransmitting the selected identifying signal with modified characteristic to the central station.

13. A transponder adapted to be selectively actuated from a larger group of transponders by selection signals transmitted from a station in first and second successive sets in which the number of signals in the second set is less than and is taken from the signals of the first set, said transponder upon actuation retransmitting interrogation signals received from said station comprising means for receiving the selection and interrogation signals, means for retransmitting the received interrogation signals, means responsive only to the successive occurrence of said first and second sets of selection signals for rendering said retransmission means operative, and circuit means responsive to said interrogation signals for producing a predetermined characteristic for said retransmitted signals to identify the actuated transponder.

14. A transponder to be selectively actuated from a larger group of transponders by selection signals transmitted from a station in first and second successive sets in which the number of signals in the second set is less than and is taken from the signals of the first set, said transponder upon actuation retransmitting interrogation signals received from said station comprising means for receiving the selection and interrogation signals, means responsive only to the successive reception of said first and second sets of selection signals for producing a gating signal, means for logically modifying the received interrogation signals in accordance with an existing set of conditions, and means responsive to said gating signal for retransmitting the logically modified interrogation signals back to the station.

15. A transponder adapted to be selectively actuated from a larger group of transponders by selection signals transmitted from a station in first and second successive sets in which the number of signals in the second set is less than is taken from the signals of the first set, said transponder upon actuation retransmitting interrogation signals received from said station comprising means for receiving the selection and interrogation signals, means responsive only to the successive reception of said first and second sets of selection signals for producing a gating signal, means for logically modifying the received interrogation signals in accordance with an existing set of conditions, means responsive to said gating signal for retransmitting the logically modified interrogation signals back to the station, and circuit means operative in response to the logically modified interrogation signals to impart to said logically modified signals a predetermined characteristic representative of the identity of the actuated transponder.

16. A transponder adapter to be selectively actuated from a larger group of transponders by a plurality of selection signals of different frequencies transmitted from a station in first and second successive sets in which the signals in the second set are less in number than and are taken from the signals in the first set, said transponder retransmitting interrogation signals received from said station upon actuation, comprising means for receiving the selection and interrogation signals, means for retransmitting the received interrogation signals, and frequency selective means responsive only to the successive occurrence of said first and second sets of selection signals for rendering said retransmitting means operative.

17. A transponder adapted to be selectively actuated from a larger group of transponders by a plurality of selection signals of different frequencies transmitted from a station in first and second successive sets in which the signals in the second set are less in number than and are taken from the signals in the first set, said transponder retransmitting interrogation signals received from said station upon actuation comprising means for receiving the selection and interrogation signals, means for retransmitting the received interrogation signals, frequency selective means responsive only to the successive occurrence or said first and second sets of selection signals for rendering said retransmitting means operative, and circuit means responsive to said interrogation signals for producing a predetermined characteristic for said retransmitted signals to identify the actuated transponder.

18. A transponder adapter to be selectively actuated from a larger group of transponders by a plurality of selection signals of different frequencies transmitted from a station in first and second successive sets in which the signals in the second set are less in number than and are taken from the signals in the first set, said transponder retransmitting interrogation signals received from said station upon actuation, comprising means for receiving the selection and interrogation signals, means for logically modifying the received interrogation signals in accordance with an existing set of conditions, means for retransmitting the logically modified interrogation signals, and frequency-selective means responsive only to the successive occurrence of said first and second sets of selection signals for rendering said retransmitting means operative.

19. A transponder adapted to be selectively actuated from a larger group of transponders by a plurality of selection signals of different frequencies transmitted from a station in first and second successive sets in which the signals in the second set are less in number than and are taken from the signals in the first set, said transponder retransmitting interrogation signals received from said station upon actuation, comprising means for receiving the selection and interrogation signals, means for logically modifying the received interrogation signals in accordance with an existing set of conditions, means for retransmitting the logically modified interrogation signals, frequency-selective means responsive only to the successive occurrence of said first and second sets of selection signals for rendering said retransmitting means operative, and circuit means operative in response to the logically modified interrogation signals to impart to said logically modified signals a predetermined characteristic representative of the identity of the actuated transponder.

20. A transponder device responsive to data bit interrogation signals comprising means responsive to a unique group of predetermined signals for actuating the transponder, means for logically modifying the data bit interrogation signals to produce true and complementary patterns thereof, means for controlling the operation of said logical modification means, means for transmitting the logically modified signals, and means for imparting a characteristic to the transmitted signals to identify the actuated transponder producing the same.

21. A transponder device responsive to data bit interrogation signals comprising means responsive to unique sets of signals of predetermined frequencies which sets occur in a predetermined order for actuating the transponder, means for logically modifying the interrogation signals to produce true and complementary patterns thereof, means for controlling the operation of said logical modification means, and means for transmitting the logically modified signals.

22. A selectively actuated transponder responsive to interrogation signals of data bit form comprising frequency selective means responsive to the successive occurrence of unique sets of signals of different frequencies for producing a conditioning signal, means responsive to said conditioning signal for producing a gating signal, circuit means for logiCally modifying the interrogation signals which appear as signals of one of the sets of signals passed by said frequency selective means, means for modulating the logically modified interrogation signals with a characteristic frequency identifying the particular transponder, means for retransmitting the signals back to the central station, and means responsive to said gating signal for controlling the retransmission of the signals back to the central station.

23. A selectively actuated transponder responsive to interrogation signals of data bit form comprising frequency selective means responsive to the successive occurrence of sets of predetermined signals for producing a conditioning signal, a recognition register conditioned by said conditioning signal for producing a gating signal, logical signal modifying means for logically modifying said interrogation signals in accordance with an existing condition, means responsive to said gating signal for selectively varying the logically modified interrogation signals to uniquely identify the transponder, and means for retransmitting the interrogation signals back to the control station.

24. A selectively actuated transponder responsive to interrogation signals of data bit form which occur as signals of first and second levels comprising means responsive to the successive occurrence of sets of predetermined signals for producing a conditioning signal, means responsive to said conditioning signal for producing a gating signal, logical signal modifying means for logically modifying the received interrogation data bit signals in accordance with an existing condition, a ringing circuit for producing tone pulses of a selected frequency in response to a modified data bit signal of one of said levels, gating means connected to said logical signal modifying means and said ringing circuit and responsive to said gating signal for applying the modified data bit signals to said ringing circuit, and means for retransmitting the tone pulses occurring in response to said modified data bit signals.

25. A selectively actuated transponder responsive to interrogation signals of data bit form which occur as signals of first and second levels comprising means responsive to the successive occurrence of sets of predetermined signals for producing a conditioning signal, means responsive to said conditioning signal for producing a gating signal, logical signal modifying means for logically modifying the received interrogation data bit signals in accordance with an existing condition, oscillator means for producing a signal of a selected frequency, modulator means, means for connecting said modulator means to said logical signal modifying means, said modulator means being responsive to said gating signal to amplitude-modulate the selected frequency signal and said modified data bit signals, and means for transmitting the modulated selected frequency signal.

26. A selectively actuated transponder responsive to interrogation signals of data bit form which occur as signals of first and second levels and also being responsive to a tone signal of a predetermined frequency comprising means responsive to the successive occurrence of sets of predetermined signals for producing a conditioning signal, means responsive to said conditioning signal for producing a gating signal, logical signal modifying means for logically modifying the received interrogation data bit signals in accordance with an existing condition, frequency selective means for selecting said tone signal of predetermined frequency modulator means connected to said logical signal modifying means, and means responsive to said gating signal for applying said tone signal of predetermined frequency to said modulator means for modulation by the logically modified data bit signals and means for retransmitting the modulated tone signal of predetermined frequency.

27. A selectively actuated transponder adapted to be used with a television receiver for determining the condition and tuning thereof, saiD transponder being responsive to data bit type interrogation signals of first and second levels comprising frequency selective means responsive to a first set of predetermined signals of different frequencies for producing a first conditioning signal, means responsive to said first conditioning signal for producing a first gating signal, a recognition register conditioned by said first gating signal for producing a second gating signal, said frequency responsive means also being responsive to a second set of predetermined signals of fewer number than said first set for producing a second conditioning signal, said gating signal means being responsive to said second conditioning signal for continuing the production of said first gating signal to hold the recognition register conditioned for producing said second gating signal, a logical signal modifying means for logically modifying the data bit interrogation signals in accordance with the condition and tuning of the television receiver, means for impressing a characteristic frequency tone onto the logically modified binary bit interrogation signals for identifying the particular transponder, means connected to said logical signal modifying means and responsive to said second gating signal for applying said logically modified interrogation signals to said tone impressing means, and means for transmitting the interrogation signals with the characteristic tone.

28. A selectively actuated transponder adapted to be used with a television receiver for determining the condition and tuning thereof, said transponder being responsive to data bit type interrogation signals of first and second levels comprising frequency selective means responsive to a first set of predetermined signals of different frequencies for producing a first conditioning signal, means responsive to said first conditioning signal for producing a first gating signal, a recognition register conditioned by said first gating signal for producing a second gating signal, said frequency responsive means also being responsive to a second set of predetermined signals of fewer number than said first set for producing a second conditioning signal, said gating signal means being responsive to said second conditioning signal for continuing the production of said first gating signal to hold the recognition register conditioned for producing said second gating signal, a logical signal modifying means for logically modifying the data bit interrogation signals in accordance with the condition and tuning of the television receiver, a ringing circuit for producing tone pulses of a selected frequency in response to a modified data bit signal of one of said levels, gating means connected to said logical signal modifying means and said ringing circuit and responsive to said second gating signal for applying the modified data bit signals to said ringing circuit, and means for retransmitting the tone pulses occurring in response to said modified data bit signals.

29. A selectively actuated transponder adapted to be used with a television receiver for determining the condition and tuning thereof, said transponder being responsive to data bit type interrogation signals of first and second levels comprising frequency selective means responsive to a first set of predetermined signals of different frequencies for producing a first conditioning signal, means responsive to said first conditioning signal for producing a first gating signal, a recognition register conditioned by said first gating signal for producing a second gating signal, said frequency responsive means also being responsive to a second set of predetermined signals of fewer number than said first set for producing a second conditioning signal, said gating signal means being responsive to said second conditioning signal for continuing the production of said first gating signal to hold the recognition register conditioned for producing said second gating signal, a logical signal modifying means for logically modifying the Data bit interrogation signals in accordance with the condition and tuning of the television receiver, oscillator means for producing a signal of a selected frequency, modulator means, means connected to said modulator means and responsive to said second gating signal for producing amplitude modulation of said selected frequency signal by the first and second levels of said modified signals, and means for transmitting the modulated selected frequency signal.

30. A selectively actuated transponder adapted to be used with a television receiver for determining the condition and tuning thereof, said transponder being responsive to data bit type interrogation signals of first and second levels and to a characteristic tone signal of a predetermined frequency comprising selective means responsive to a first set of predetermined signals of different frequencies for producing a first conditioning signal, means responsive to said first conditioning signal for producing a first gating signal, a recognition register conditioned by said first gating signal for producing a second gating signal, said frequency responsive means also being responsive to a second set of predetermined signals of fewer number than said first set for producing a second conditioning signal, said gating signal means being responsive to said second conditioning signal for continuing the production of said first gating signal to hold the recognition register conditioned for producing said second gating signal, a logical signal modifying means for logically modifying the data bit interrogation signals in accordance with the condition and tuning of the television receiver, frequency selective means for selecting said characteristic tone signal of predetermined frequency, modulator means connected to said logical signal modifying means, means responsive to said second gating signal for producing modulation by said modulator of the selected predetermined frequency tone signal and said modified interrogation bit signals in accordance with the first and second levels thereof, and means for transmitting the modulated signals.

31. An interrogated transponder responsive to a first interrogation signal comprising means for receiving said first interrogation signal, means responsive to said first interrogation signal for producing a delayed version thereof, means for modifying the received first interrogation signal and the delayed version thereof in accordance with a given condition, and means for retransmitting the modified interrogation signals.

32. An interrogated transponder responsive to be actuated by first and second signals to transmit a reply to interrogation signals comprising first and second means for respectively receiving said first and second signals, first and second delay means respectively connected to said first and second receiving means for producing delayed versions of said first and second signals, means responsive to the occurrence of said first and second signals and to the delayed versions of the first and second signals for producing a conditioning signal, and means responsive to said conditioning signal for retransmitting the interrogation signals.

33. An interrogated transponder responsive to be actuated by first and second signals and to transmit a reply to interrogation signals which appear as at least one of said first and second signals comprising first and second means for respectively receiving said first and second signals, first and second delay means respectively connected to said first and second receiving means for producing delayed versions of said first and second signals, means responsive to the occurrence of said first and second signals and to the delayed versions thereof for producing a conditioning signal, means for modifying the interrogation signals appearing as at least one of said first and second signals and the delayed versions thereof in accordance with a given condition, and means responsive to said conditioning signal for transmitting the modified interrogatiOn signals.

34. A system for selectively interrogating final groups of transponders in which each interrogated final group exists as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station:

means for transmitting in order a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, where k is less than n, and a number of interrogation signals; and

further comprising means at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, and means responsive to said actuating signal for retransmitting the interrogation signals.

35. A system for selectively interrogating final groups of transponders in which each interrogated final group exists as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station:

means for transmitting in order a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, where k is less than n, and a number of interrogation signals; and

further comprising means at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, means responsive to the condition of equipment associated with a respective transponder for modifying the interrogation signals, and means responsive to said actuating signal for transmitting the modified interrogation signals.

36. A system for selectively interrogating final groups of transponders in which each interrogated final group exists as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station:

means for transmitting in order a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, where k is less than n, and a number of interrogation signals; and

further comprising means at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, means at each transponder for imparting a characteristic to the interrogation signals for identifying the individual transponders in a final group, and means responsive to said actuating signal for transmitting the interrogation signals with the identifying characteristic thereon.

37. A system for selectively interrogating final groups of transponders in which each interrogated final group exists as part of a major group, there being a number of major groups of transponders operating with the system comprising at a central station:

means for transmitting in order a first set of n selection signals from an available number of m selection signals, where m is greater than n;

a second set of k selection signals selected from said first set of n signals, where k is less than n, and a number of interrogation signals; and

further comprising means at each transponder of a respective final group responsive to predetermined first and second sets of n and k signals for producing a transponder actuating signal, means at each transponder responsive to the condition of equipment associated with a respective transponder for modifying the interrogation signals, means responsive to said actuating signal for transmitting the modified interrogation signals, and means for impArting a characteristic to the modified interrogation signals for identifying the individual transponders in a final group.

38. A system for selectively interrogating successive groups of transponders from a greater number of transponders to determine information relating to an existing condition of apparatus associated with a respective transponder in the interrogated group, comprising at a central station;

means for transmitting in order a first set of n tone signals of different frequencies from an available number of m tone signals of different frequencies, where m is greater than n;

a second set of k tone signals selected from said n tone signals, where k is less than n, and a number of interrogation signals in data bit form selected from the n tone signals; and

comprising at each transponder a recognition register;

frequency selective means in each group of transponders to be selectively interrogated responsive to a predetermined first set of n tone signals for producing a gating signal to condition said recognition register, said frequency selective means also being responsive to a predetermined second set of k tone signals for producing a gating signal to hold said recognition register conditioned;

means responsive to the conditioning of the recognition register by said second set of k tones for producing in response to the interrogation signals tone signals characteristic of the transponder in the selectively interrogated group, and means for retransmitting the characteristic tone signals to the central station.

39. A system as set forth in claim 38 wherein each transponder also has means for logically modifying the data bit interrogation signals in accordance with the existing condition of the apparatus associated with each transponder.

40. A system for selectively interrogating final groups of transponders to determine information relating to an existing condition of apparatus associated with an individual transponder in each interrogated final group, each said interrogated final group existing as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station;

means for transmitting in order a first set of n tone signals of different frequencies from an available number of m tone signals of different frequencies, where m is greater than n;

a second set of k tone signals selected from said m signals, where k is less than m; and

tone signals selected from said first set of n tone signals as interrogation signals; and

further comprising frequency responsive means at each transponder in a respective major group responsive to a predetermined first set of n tone signals;

frequency responsive means at each transponder in a respective final group existing within a major group responsive to a predetermined second set of k tone signals, and means at each transponder responsive to the application of the predetermined first and second sets of n and k tone signals to the frequency responsive means for actuating the transponders in a final group to transmit information signals relating to the condition of the associated apparatus in response to the interrogation signals.

41. A system as set forth in claim 40 wherein each transponder in a final group also has means for impressing an identifying characteristic onto the transmitted information signals corresponding to the identity of the individual transponder within the final group.

42. A system for selectively interrogating final groups of transponders to determine information relating to an existing condition of apparatus associated with an individual transponder in each interrogated final group, each of said interrogated final group existing as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station:

means for transmItting in order a first set of n tone signals of different frequencies from an available number of m tone signals of different frequencies, where m is greater than n;

a second set of k tone signals selected from said m signals, where k is less than m; and

tone signals selected from said first set of n tone signals as interrogation signals in data bis form; and

further comprising frequency responsive means at each transponder in a respective major group responsive to a predetermined first set of n tone signals;

frequency responsive means at each transponder in a respective final group existing within a major group responsive to a predetermined second set of k tone signals, means at each transponder for logically modifying received data bit interrogation signals in accordance with the condition of the equipment associated with a respective transponder, and means at each transponder responsive to the application of the predetermined first and second sets of n and k tone signals to the frequency responsive means for actuating the transponders in the final group responsive to these predetermined first and second sets of tone signals for retransmitting the logically modified interrogation signals to the central station.

43. A system as set forth in claim 42 wherein each transponder in a final group also has means for impressing an identifying characteristic onto the retransmitted interrogation signals corresponding to the identity of the individual transponder within the final group.

44. A subscriber television system in which each subscriber has a receiver for receiving television programs and a transponder for transmitting back to a central station information concerning the condition and tuning of the associated receiver the transponders of said system to be interrogated in final groups with each said interrogated final group existing as part of a major group, there being a number of major groups of transponders operating with the system, comprising at a central station:

means for transmitting first sets of n tone signals of different frequencies;

second sets of k tone signals of different frequencies, where k is less than n; and

tone signals in data bit form as interrogation signals; and

further comprising frequency responsive means at each transponder in a respective major group responsive to a predetermined first set of n tone signals for producing a conditioning signal, frequency responsive means at each transponder in a final group existing in a major group responsive to a predetermined second set of k tone signals for continuing the production of the conditioning signal, gating means responsive to be conditioned by said conditioning signal, means for logically modifying the received interrogation signals in accordance with the condition and tuning of the receiver associated with each transponder in the final group being interrogated in accordance with the transmission of the predetermined first and second sets of signals , means responsive to said logically modified signals and to the conditioning of the gating means by a predetermined second set of k tones for producing tone signals characteristics of the transponder in the interrogated final group, and means for retransmitting the characteristic tone signals back to the central station.

45. The method of selectively interrogating final groups of transponders from a larger number of transponders in response to predetermined sets of received selection signals comprising the steps of successively transmitting predetermined sets of n selection signals, selecting a predetermined major group of transponders by each predetermined set of n selection signals, transmitting predetermined sets of k selection signals, where k is less than n, selecting by each predetermined set of k selection signals a final group of transponders to be interrogated within a predetermined major group, And interrogating each transponder of a selected final group.

46. The method of selectively interrogating final groups of transponders from a larger number of transponders in response to predetermined sets of received selection signals comprising the steps of successively transmitting predetermined sets of n selection signals from an available number of m selection signals, selecting a predetermined major group of transponders by each predetermined set of n selection signals, transmitting predetermined sets of k selection signals taken from the n selection signals, where k is less than n, selecting by each predetermined set of k selection signals a final group of transponders to be interrogated within a predetermined major group, transmitting interrogation signals, and transmitting information signals from each selected final group of transponders in response to the interrogation signals.

47. The method of selectively interrogating a final group of transponders from a larger number of transponders wherein each transponder is responsive to be actuated to retransmit interrogation signals in response to predetermined sets of received selection signals comprising the steps of transmitting to said number of transponders predetermined first sets of n selection signals, selecting a predetermined major group of transponders by each predetermined first set of n selection signals, transmitting to each selected major group of transponders a predetermined second set of k selection signals of lesser number than the signals in said first set, selecting from a selected major group of transponders by said predetermined second set of k selection signals a final group of transponders to be interrogated, utilizing the received interrogation signals at the selected final group of transponders to produce information, transmitting another predetermined second set of k selection signals different from the first mentioned second set of k signals, and selecting by said another set of k selection signals a second final group of transponders to be interrogated in the selected major group of transponders.

48. The method of selectively interrogating final groups of transponders from a larger number of transponders wherein each transponder is responsive to be actuated to retransmit interrogation signals in response to predetermined sets of successively received selection signals comprising the steps of transmitting a first set of n selection signals from an available number of m selection signals, selecting a first major group of transponders by said first set of n selection signals, transmitting a second set of k selection signals taken from the first set of n selection signals and being of lesser number than the n selection signals in said first set, selecting from said first major group of transponders by said second set of k selection signals the final group of transponders to be interrogated, transmitting interrogation signals, modifying the received interrogation signals at the selected group of transponders in accordance with the condition of equipment being monitored, and retransmitting modified interrogation signals with a unique characteristic in accordance with the identity of a particular transponder within the selected final group.

49. A transponder for a data acquisition system comprising means for responding to an individual interrogation signal for rendering the transponder operative for transmitting the individual interrogation signal through the transponder, means coupled to the responding means for receiving the interrogation signal and operating on same in accordance with the operating status of a station of the data acquisition system, and means coupled to the latter mentioned means for imparting a station identification characteristic to the received signal whereby the resulting signal identifies the operating status of the station and the station interrogated.

50. A transponder for a data acquisition system as defined in claim 49 wherein the means for operating on the interrogation signal includes switching means for tuning a station to different signals and modifying the interrogation signal in accordance with the tuned condition of the station.

51. A system for acquiring data from a plurality of remote stations at a central station comprising a plurality of remote stations, each remote station including a transponder, means at a central station for transmitting individual station interrogation signals to the remote stations and receiving the interrogation signals from the stations, each of said transponders comprising means for responding to an individual interrogation signal for actuating the transponder in response to the reception of the individual interrogation signal to couple the interrogation signal through the transponder for return to the transmitting means, means coupled to the responding means for receiving the individual interrogation signal and operating on same in accordance with the operating status of the station, and means coupled to the latter mentioned means for imparting a station identification characteristic to the received signal to thereby indicate by means of the resulting interrogation signal received at the central station the operating status and the identification of the interrogated station.