Improved receiver selecting (voting) system

• US 4,013,962 A
• Filed: 08/14/1975
• Issued: 03/22/1977
• Est. Priority Date: 08/14/1975
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Beseke, Kermit Myles, Ramsland, David Gordon, Stedman, Robert Bruce
• Primary Examiner(s): Griffin, Robert L.
• Assistant Examiner(s): Ng, Jin F.
• Application Number:
  US05/604,562
• Time in Patent Office: 586 Days
• Field of Search: 325/2, 325/31, 325/56, 325/62, 325/64, 325/65, 325/322, 325/301-306, 325/323, 325/326, 325/348, 325/399, 325/403, 325/478, 325/402, 325/410
• US Class Current: 455/135
• CPC Class Codes: H04B 7/082 selecting best antenna path

Abstract

An improved receiver voting system is disclosed in which the lowest noise audio signal produced by a number of different radio receivers is selected and coupled to a monitoring speaker. Each receiver receives signals from a transmitter and produces either corresponding audio signals or squelch indicating status tones which are then transmitted to a voting (selecting) control center by telephone communication lines. The voting control center then selects the unsquelched receiver audio signal having the lowest noise level and couples this signal to a monitoring speaker.

The voting center indicates which receiver is supplying the selected signal and therefore identifies the most favorable receiver to transmitter signal path. Parallel squelch circuits in each receiver provide for the initial selection of the strongest received signal while preventing the existence of an irratating "squelch tail." Automatic gain control circuitry in the voting control center compensates for loss variations between the different transmission lines coupling signals to the voting control center. Status tone decoders in the voting control center prevent the selection of the squelch indicating status tone as the receiver signal having the lowest noise level. The voting control center has circuitry for switching in a status tone notch filter and changing the response time of the status tone decoder whenever a squelch indicating status tone is anticipated by the control center. Each receiver produces an audio pause which precedes the production of a squelch indicating status tone, and this enables the voting control center to anticipate the status tone and to rapidly respond to its occurrence.

Claims

1. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and substantially corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

a plurality of transmission line means for coupling the output signal of each of said plurality of receivers to a comparison location;

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals; and

load means for receiving the selected output signal;

each of said output signal producing means of said receivers including,

variable squelch means for delaying by a first predetermined time the response of said output signal producing means to a change in the magnitude of said received input signals from below to above said predetermined level, said first predetermined time being related to the amount that the magnitude of said received input signals is above said predetermined level, and

delay means for creating, in response to a change in the magnitude of said input signals from above to below said predetermined level, an output signal pause which precedes in time the production of said output signal which corresponds to said status signal;

said voting circuit means including,

decoder means for producing, when said detector means is enabled, detect signals associated with any of said output signals which correspond to said status signal for at least a minimum time duration, said detect signals being used in preventing the selection of any output signal which corresponds to said status signal,

loss of activity means for detecting a loss of signal activity in each of said output signals and producing associated enable signals by comparing each of said output signals with an associated signal related to the background noise level of said output signal,

line failure detector means coupled to said loss of activity means for preventing the selection of any of said output signals in which a detected loss of signal activity exists for at least a predetermined duration of time,

circuitry for coupling said loss of activity detector means to said decoder means and, in response to a pause being detected in any of said output signals, enabling said decoder means for any of said output signals which include a detected pause,

filter means coupled to said loss of activity means and between said load means and said transmission line means for inserting a status signal filter between said load means and said transmission line means in response to a signal pause being detected by said loss of activity detector, said status signal filter preventing the load means from responding to a selected output signal having a detected audio pause followed by said status signal, and

signal loss equalization means for separately amplifying each of said received output signals by a gain factor which substantially compensates for the magnitude variation of said received output signals contributed by said transmission line means, whereby said voting circuit means compares said compensated output signals in order to select the output signal having the optimum signal quality level.

2. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and substantially corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

each receiver including a delay means for creating, in response to the magnitude of said input signals changing from above to below said predetermined level, an output signal pause which precedes in time the production of said output signal which corresponds to said status signal;

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location;

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals; and

load means for receiving the selected output signal;

said voting circuit means including a pause detector means for detecting the presence of a signal pause in the selected output signal, and

filter means coupled to said pause detector means and between said load means and said transmission line means for inserting a status signal filter between said load means and said transmission line means in response to a signal pause being detected by said pause detector, said status signal filter preventing the load means from responding to a status signal portion of the selected output signal in which a detected audio pause is followed by said status signal.

3. An improved receiver voting system according to claim 2 which includes status decoder means for producing detect signals associated with any of said output signals which correspond to said status signal, and circuitry coupled to said filter means and said decoder means for maintaining the insertion of said filter means in response to the production of said detect signals.

4. An improved receiver voting system according to claim 2 wherein said signal voting circuit means includes status signal decoder means for producing detect signals associated with any of said output signals which correspond to said status signal, said detect signals preventing said signal voting circuit means from selecting an output signal which corresponds to said status signal.

5. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

each of said receivers including a variable squelch means for delaying by a first predetermined time the response of said output signal producing means to a change in the magnitude of said received input signals from below to above said predetermined level, said first predetermined time being related to the amount that the magnitude of said received input signals is above said predetermined level;

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location;

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals, whereby said variable squelch means results in said receiver voting system initially selecting the strongest received input signals by producing the smallest predetermined time delay for the strongest received input signals.

6. An improved receiver voting system for selecting at least one of several signals to be monitored said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location; and

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers, amplifying and selecting, for monitoring purposes, the one of said amplified output signals which has the optimum signal quality level of all of the received and amplified output signals which correspond to said input signals;

said voting circuit means including signal loss equalization means for producing said amplified output signals by separately amplifying each of said received output signals by a gain factor which substantially compensates for the magnitude variation of said received output signals contributed by said transmission line means, said loss equalization means including means for amplifying each of said received output signals by a variable gain factor for maintaining the magnitude of the amplified output signal at a constant level in response to said amplified output signal corresponding to said status signal and means for amplifying each of said received output signals by a constant gain factor in response to said output signal substantially corresponding to said input signals.

7. An improved receiver voting system according to claim 6 wherein said constant gain factor corresponds to the variable gain factor which existed just before said output signal was detected as corresponding to said input signals.

8. An improved receiver voting system according to claim 7 wherein said loss equalization means includes a status signal decoder means coupled to said AGC means, said decoder means receiving each of said output signals, detecting when said output signals correspond to status signals and producing a detect signal for controlling the gain of said AGC means, whereby the occurrence of said detect signal fixes the gain of said AGC means at the variable gain factor which existed just prior to the production of said detect signal.

9. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location; and

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers, comparing said received output signals and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals;

said voting circuit means including,

means for receiving each of said output signals and producing associated signals related to the background noise level of each of said output signals,

loss of activity means coupled to said associated noise level signal producing means for detecting a loss of signal activity in each of said output signals by comparing each of said output signals with the associated signal related to the background noise level of said output signal, and

line failure detector means coupled to said loss of activity means for preventing the selection of any of said output signals in which a detected loss of signal activity exists for at least a predetermined duration of time.

10. An improved receiver voting system according to claim 9 wherein said voting circuit means includes comparison means coupled to said associated noise level signal producing means for receiving each of said associated background noise level signals and comparing them for selecting the output signal to be monitored.

11. A signal decoding system for a received signal having information signals followed by a pause in activity and then followed by a status coding tone, said system rapidly identifying a proper status coding tone while effectively ignoring any information signals that may accidently correspond to said status coding tone, said system comprising:

decoder means for producing detect signals associated with said received signal in response to said received signal substantially corresponding to said status coding tone for at least a minimum time, said detect signals indicating the presence of a proper status coding tone;

loss of signal activity detector means for detecting the presence of pause in the activity of said received signal and producing a pause detect signal; and

control means for coupling said pause detect signal from said loss of activity detector means to said decoder means for reducing said minimum time duration of said decoder means in response to a pause detection by said loss of activity detector means, whereby said decoder means is prevented from rapidly responding to information signals which momentarily correspond to said status coding tone and said decoder means is permitted to more rapidly respond to any status coding tones which are preceded by a pause.

12. An improved transmission line loss compensating system comprising:

at least one receiver means for producing an output signal which includes sequential information and status signals, said status signals having a constant amplitude;

transmission line means for coupling said output signal to a location; and

circuit means located at said location for receiving said output signal and amplifying said output signal by a gain factor to compensate for any signal loss due to said transmission means,

said circuit means including AGC means for amplifying said output signal by a variable gain factor to maintain the amplified output signal at a constant predetermined amplitude level in response to said output signal being detected as corresponding to said status signals, said AGC means including circuitry for amplifying said output signal by a fixed gain factor in response to said output signal being detected as corresponding to said information signals, said fixed gain factor being substantially the same as the variable gain factor which existed just prior to said output signal being detected as corresponding to said information signals, whereby the transmission line loss is exactly compensated for when said output signal corresponds to said status signal and the loss is substantially compensated for when said output signal corresponds to said information signals.

13. An improved communication decoding system for compensating for the response time of a decoder, said system comprising:

at least one receiver means for producing an output signal which includes information signals followed by an anticipation signal and then followed by a code signal; and

circuit means for receiving said output signal and selectively coupling said output signal to a load;

said circuit means including,

decoder means for producing at least one detect signal in response to said output signal corresponding to said code signal for at least a minimum duration of time, said detect signal adaptable for use by said circuit means to prevent said load from receiving said code signal,

detector means for detecting the occurrence of said anticipation signal in said output signal, and

filter means coupled to said load and said detector means for preventing said load from receiving said code signal for a predetermined time after said anticipation signal has been detected, whereby said load can receive said information signal portion of said output signal, is prevented from receiving said code signal portion of said output signal during said minimum duration of time of said decoder means by said anticipation signal detector means and said filter means, and can be prevented from receiving said code signal portion of said output signal after said minimum duration of time by utilization of said decoder code detect signal.

14. An improved communication decoding system according to claim 13 wherein said anticipation signal comprises a pause in output signal activity and wherein this pause is detected by said detector means.

15. An improved communication decoding system according to claim 14 wherein said filter means only prevents said load from receiving said code signal portion of said output signal and otherwise permits said load to receive said output signal.

16. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

each of said output signal producing means of said receivers including a variable squelch means for delaying by a first predetermined time the response of said output signal producing means to a change in the magnitude of said received input signals from below to above said predetermined level, said first predetermined time being related to the amount that the magnitude of said received input signals is above said predetermined level;

each of said output signal producing means of said receivers including rapid squelch means for producing the termination of said output signal which corresponds to said input signals within a second predetermined time duration after the magnitude of said input signal has fallen below a preset level, said second predetermined time being substantially less than said first predetermined time;

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location;

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals.

17. An improved receiver voting system according to claim 16 wherein said variable and rapid squelch means are coupled in parallel to a logic combining gate which produces a control voltage for an audio squelch gate.

18. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

each of said output signal producing means of said receivers including a variable squelch means for delaying by a first predetermined time the response of said output signal producing means to a change in the magnitude of said received input signals from below to above said predetermined level, said first predetermined time being related to the amount that the magnitude of said received input signals is above said predetermined level;

each output signal producing means of said receivers includes a coded squelch means coupled in parallel with said variable squelch means to a logic combining gate means for delaying the production of said output signal which corresponds to said input signals until a predetermined code has been identified as existing on said received input signals,

a plurality of transmission line means for coupling the output signals of each of said plurality of receivers to a comparison location;

signal voting circuit means located at said comparison location for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals.

19. A signal decoding system for a received signal having information signals followed by a pause in activity and then followed by a status coding signal, said system rapidly identifying a proper status coding signal while effectively ignoring information signals which may accidently correspond to said status coding signal, said system comprising:

decoder means for producing, when said decoder means is enabled, detect signals associated with said received signal in response to said received signal substantially corresponding to said status coding signal for at least a minimum duraton of time;

loss of signal activity detector means for detecting the presence of a pause in the activity of said received signal; and

control means coupled between said loss of activity detector means and said decoder means for enabling said decoder means in response to a detection of a pause in activity by said loss of activity detector means, whereby said decoder means is prevented from responding to information signals which may correspond to said status coding signal for said minimum duration while said decoder means is permitted to respond to a status coding signal of said minimum duration which is preceded by a audio pause.

20. A signal decoding system according to claim 19 wherein said status coding signal comprises at least one audio tone and said information signals comprise audio tones.

21. An improved receiver voting system for selecting at least one of several signals to be monitored, said system comprising:

a plurality of receivers, each receiver including means for receiving input signals and producing an output signal having a pause in activity, said output signal substantially corresponding to said input signals in response to said input signals having a magnitude equal to and above a predetermined level and substantially corresponding to a predetermined status signal in response to the magnitude of said input signals being below said predetermined level;

a plurality of transmission line means for coupling the output signal of each of said plurality of receivers to a comparison location; and

signal voting circuit means located at said comparison located for receiving the output signals of each of said receivers and selecting, for monitoring purposes, the one of said output signals which has the optimum signal quality level of all of the received output signals which correspond to said input signals;

said voting circuit means including,

decoder means for producing, when said decoder means is enabled, detect signals associated with any of said output signals which correspond to said status signal for at least a minimum time duration, said detect signals adaptable for use in preventing the selection of any output signal which corresponds to said status signal,

loss of activity decoder means for detecting the presence of a pause in the activity of any of the output signals, and

circuitry for coupling said loss of activity detector means to said decoder means and, in response to a pause being detected in any of said output signals, enabling said decoder means for any of said output signals which include a detected pause, whereby said decoder means will respond in said minimum time duration to a status signal following said detected pause.

22. An improved receiver voting system according to claim 21 wherein each of said receiver output signal producing means includes circuitry for creating said pause in said output signal in response to the magnitude of said received input signals falling below said predetermined level.