Answer detection method and apparatus for coin telephone sets
First Claim
1. In a telephone station including a 4-wire to 2-wire hybrid circuit interconnecting a transmitting microphone and a receiver circuit to a wire pair, apparatus for detecting that a called party has answered a call by measuring electrical energy present on the wire pair, said detecting apparatus including means responsive to the magnitude of the electrical energy, above a frequency of approximately 200 Hz and exceeding a first predetermined threshold,characterized by:
- first means for inhibiting the indication of called party answer in response to the detection of a sequence of three predetermined tones; and
second means for inhibiting the indication of called party answer in response to the detection of energy exceeding a second predetermined threshold in the frequency band substantially between 200 Hz and 700 Hz.
1 Assignment
0 Petitions
Accused Products
Abstract
A coin operated telephone station is provided with apparatus for detectinghen a called party has answered a call (initiated at the coin operated telephone station) by the measurement of incoming signal energy on the telephone line. The apparatus includes hardware and software that cooperate in providing efficient and reliable detection of called party answer for the purpose of accurately charging telephone users. A microprocessor samples the output from each of three specialized energy detectors every 20 milliseconds to determine whether called party answer has occurred. The energy detectors include: (1) call progress tones in the frequency band 200-700 Hz approximately; (2) special information tones; and (3) broadband energy in the frequency band above 200 Hz. Additionlly, the time duration of the call progress tones and the quiet intervals between them are measured and used in the answer detection process. Signal energy from the calling party in the 200-700 Hz frequency band is filtered from the transmitting path by a 1200 Hz high-pass filter until called party answer occurs. Such filtering precludes a user from interfering with the detection process while permitting a limited amount of information to be tranmitted in the event that the answer detector is slow to operate.
41 Citations
15 Claims
-
1. In a telephone station including a 4-wire to 2-wire hybrid circuit interconnecting a transmitting microphone and a receiver circuit to a wire pair, apparatus for detecting that a called party has answered a call by measuring electrical energy present on the wire pair, said detecting apparatus including means responsive to the magnitude of the electrical energy, above a frequency of approximately 200 Hz and exceeding a first predetermined threshold,
characterized by: -
first means for inhibiting the indication of called party answer in response to the detection of a sequence of three predetermined tones; and second means for inhibiting the indication of called party answer in response to the detection of energy exceeding a second predetermined threshold in the frequency band substantially between 200 Hz and 700 Hz. - View Dependent Claims (2, 3)
-
-
4. In a telephone station for connection to a telephone network by a wire pair, apparatus for indicating called party answer comprising:
-
energy detecting means, responsive to the magnitude of bursts of electrical energy on the wire pair in the frequency band substantially between 200 and 700 Hz exceeding a predetermined threshold, for indicating the presence of 200-700 Hz energy; first timing means, responsive to said energy detecting means, for measuring the time duration of successive bursts of electrical energy in the 200-700 Hz band and providing an output signal when the time duration of one of the energy bursts is substantially greater than the time duration of a previously measured energy burst, provided that the previously measured energy burst is not the first burst of energy in the 200-700 Hz frequency band; and answer indicating means, responsive to the output signal from the first timing means, for providing an indication of called party answer. - View Dependent Claims (6, 7, 8)
-
-
5. In a telephone station for connection to a telephone network by a wire pair, apparatus for indicating called party answer comprising:
-
energy detecting means, responsive to the magnitude of bursts of electrical energy on the wire pair in the frequency band substantially between 200 and 700 Hz exceeding a predetermined threshold, for indicating the presence of 200-700 Hz energy; first timing means, responsive to said energy detecting means, for measuring the time duration of successive bursts of electrical energy in the 200-700 Hz band and providing an output signal when the time duration of one of the energy bursts is substantially less than the time duration of a previously measured energy burst; and answer indicating means, responsive to the output signal from the first timing means, for providing an indication of called party answer.
-
-
9. In a pay telephone station controlled by a microprocessor having one or more software programs for detecting called party answer, the telephone station being connected to a telephone network over a wire pair and including coin holding and storage apparatus,
characterized by: -
energy measurement means for providing an output signal to the microprocessor when electrical energy on the wire pair, in a frequency band between 200 Hz and 700 Hz, exceeds a predetermined threshold; first timing means, responsive to the output signal from the energy measurement means, for calculating the time duration of said output signal; means for storing one or more of the time durations calculated by the first timing means; first software program means, responsive to the stored time durations for generating a called party answer signal when one of said time durations is at least 20% less than a prior time duration; means for transferring coins from the coin holding apparatus to the coin storage apparatus in response to the called party answer signal. - View Dependent Claims (10, 11)
-
-
12. In a telephone station for connection to a telephone network by a wire pair, a method for indicating called party answer comprising the steps of:
-
measuring the magnitude of bursts of electrical energy on the wire pair in the frequency band substantially between 200 Hz and 700 Hz; calculating the time duration of the bursts of electrical energy in the 200-700 Hz frequency band whose magnitude exceeds a predetermined threshold; and generating a called party answer signal when the time duration of one of the bursts of electrical energy is at least 20% less than the time duration of a prior burst. - View Dependent Claims (13)
-
-
14. In a pay telephone station including a hybrid circuit for interconnecting a telephone network to a transmitting microphone and to a receiver circuit, a method for indicating called party answer comprising the steps of:
-
(i) measuring the magnitude of electrical energy delivered to the receiver circuit in the frequency range above approximately 200 Hz; (ii) measuring the magnitude of electrical energy delivered to the receiver circuit in the frequency band substantially between 200 Hz and 700 Hz; (iii) detecting a sequence of three tones on the wire pair at frequencies of 950 Hz, 1400 Hz, and 1800 Hz respectively; and (iv) generating a called party answer signal when the magnitude measured in step (i) exceeds a first predetermined threshold, unless the magnitude of energy measured in step (ii) exceeds a second predetermined threshold, or unless tones are detected in accordance with step (iii). - View Dependent Claims (15)
-
Specification