Synchronous ring detector for station carrier telephone systems

• US 4,081,609 A
• Filed: 01/28/1977
• Issued: 03/28/1978
• Est. Priority Date: 01/28/1977
• Status: Expired due to Term

• Current Assignee: Reliance Telecommunications Electronics Company
• Original Assignee: Reliance Telecommunications Electronics Company
• Inventors: Beene, Gerald Wayne, Martin, Hubert C. Jr.
• Primary Examiner(s): Claffy, Kathleen H.
• Assistant Examiner(s): Popek, Joseph A.
• Application Number:
  US05/763,520
• Time in Patent Office: 424 Days
• Field of Search: 179/2.5 R, 179/84 R, 179/84 SS, 179/15 FD, 179/15 BP, 325/55, 325/64
• US Class Current: 370/485
• CPC Class Codes: H04M 19/04 the ringing-current being generated at the substations

Abstract

A plural channel amplitude modulated station carrier signalling circuit in which an incoming call for a subscriber served by the station carrier system is sensed at the called subscriber'"'"'s subscriber channel terminal circuit by synchronously detecting a signal which originates from a central office to signal the incoming call for the subscriber.

Claims

1. A plural channel amplitude modulated station carrier telephone system comprising subscriber terminal means providing service to a plurality of subscribers and adapted to be connected to the subscribers'"'"' telephones, said subscriber terminal means including a plurality of signal-responsive circuits corresponding in number to said plurality of subscribers and each assigned to a different one of said subscribers for ringing the assigned subscriber'"'"'s telephone, and signalling means including circuit means at said subscriber terminal means, said signalling means being responsive to an incoming call for any one of said subscribers to apply two separate synchronized signals of the same pre-selected frequency to the signal-responsive circuit that is assigned to the called subscriber, each of said signal-responsive circuits having (a) a synchronous detector rendered effective by one of said two signals for synchronously detecting the other of said two signals and (b) means responsive to the synchronous detection of the other of said signals by said detector for applying a ringing signal to cause ringing of its assigned subscriber'"'"'s telephone.

2. A method of signalling an incoming call to a subscriber serviced by a plural channel amplitude modulated station carrier telephone system, comprising the steps of transmitting a pilot carrier signal from a central office, transmitting from the central office a plurality of frequency division multiplexed channel carrier signals each assigned to a different one of the subscribers served by the station carrier telephone system, modulating both the pilot carrier signal and the channel carrier signal assigned to the subscriber being called with a signalling tone of pre-selected frequency, separately recovering the signalling tone modulations from the transmitted pilot and channel carrier signals, utilizing the recovered signalling tones to synchronously detect one of the signalling tones, and causing the called subscriber'"'"'s telephone to be rung in response to the synchronous detection of said one of said recovered tones.

3. A plural channel amplitude modulated station carrier telephone system providing service to the telephones of a plurality of subscribers and comprising means located at a central office for transmitting a plurality of frequency division multiplexed channel carrier signals, each of said channel carrier signals being assigned to a different one of said telephones, means at said central office for amplitude modulating each channel carrier signal with a voice frequency intelligence signal, a plurality of subscriber transmitting and receiving terminal circuits, transmission line means providing for the transmission of the channel carrier signals to said subscriber terminal circuits, each of said subscriber terminal circuits having a receiver tuned to receive a different pre-selected one of said channel carrier signals and adapted to be connected to the telephone that the channel carrier signal if assigned to, , means at said central office for transmitting a pilot carrier signal over said transmission line means, means responsive to an incoming call for any one of said subscribers for modulating both of said pilot carrier signal and the channel carrier signal assigned to the called subscriber'"'"'s telephone with a ringing signal of pre-selected frequency, pilot carrier signal receiver means located at the end of said transmission line means remote from said central office for receiving said pilot carrier signal and having a circuit for demodulating said pilot carrier signal and for recovering the ringing signal modulated thereon, the receiver of each of said subscriber terminal circuits having (a) first circuit means for demodulating the received one of said channel carrier signals and recovering the ringing signal modulated thereon, (b) a synchronous detector electrically connected to said circuit of said pilot carrier receiver means and to the first circuit means for synchronously detecting the ringing signal recovered by said circuit of said pilot carrier signal receiver means and said first circuit means, and (c) further circuit means electrically connected to the synchronous detector and responsive to the synchronous detection of said ringing signal by the synchronous detector for ringing the called subscriber'"'"'s telephone .

4. A plural channel amplitude modulated station carrier system for serving a plurality of subscribers and comprising a plurality of first terminal circuits located at a central office and each having a transmitter for transmitting one of a plurality of frequency division multiplexed channel carrier signals corresponding in number to the number of said first terminal circuits, each of the channel carrier signals being assigned to a different one of said subscribers to provide service for the associated subscriber, means located at said central office for providing an additional carrier signal of pre-selected frequency that is different from the frequencies of said channel carrier signals, a plurality of subscriber transmitter and receiver terminal circuits located remotely from said central office and adapted to be connected to the subscriber'"'"'s telephones, signal receiver means located remotely from said central office, signal transmission means for transmitting said channel carrier signals to said subscriber terminal circuits and said additional carrier signal to said receiver means, means at said central office for supplying an a.c. ringing signal of pre-selected frequency, means for modulating said additional carrier signal with said ringing signal, each of said first terminal circuits having means for modulating its channel carrier signal with said ringing signal in response to an incoming call for the subscriber served by its channel carrier signal, said signal receiver means being tuned to receive said additional carrier signal and having a circuit for recovering the ringing signal modulated onto said additional carrier signal, and each of said subscriber terminal circuits being tuned to receive a different pre-selected one of said channel carrier signals and including (a) means for demodulating the received one of said channel carrier signals (b) means for filtering the signal components resulting from the demodulation of the received one of said channel carrier signals by said demodulating means to recover the ringing signal when it is modulated onto the received channel carrier signal, (c) a synchronous detector electrically connected to said filtering means and to said circuit of said signal receiver means for synchronously detecting said ringing signal whenever it is simultaneously modulated onto the received one of said channel carrier signals, and said additional carrier signal, and (d) means responsive to the detection of said ringing signal by said synchronous detector for ringing the telephone of the subscriber served by the received channel carrier signal.