Patent US3725593A successfully refreshed from Google Patents.
US3725593A
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Pcm telecommunication system with standby clock
Assignee: Italtel SpA
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Filing: 1972-02-22
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Granted: 1973-04-03
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Expires: 1992-02-22
Abstract
Abstract At a main terminal connected to a remote terminal by way of a PCM signal path, a master clock controls the multiplexing of incoming messages from local lines for transmission over an outgoing line of that path to the remote terminal in a bipolar code enabling extraction of the clock frequency at the remote terminal. A discriminator at the main terminal continuously checks the operation of the master clock and, if that operation is normal, causes the transmission of a verification bit over the outgoing line to the remote terminal in an assigned time slot of a service channel of a period message frame; at the remote terminal, a detector responds to either the absence of the verification bit or the nonarrival of message signals to activate a standby clock controlling the sending of composite messages to the main terminal over an incoming line of the signal path. An extractor at the main terminal, connected to that incoming line, delivers the reconstituted pulses of the standby clock to the multiplexer in lieu of the output of the master clock if the latter operates improperly or not at all, as determined by the associated discriminator; a similar discriminator at the remote terminal may insert a corresponding verification bit into a service slot of a message frame transmitted to the main terminal to establish the correct functioning of the standby clock.
Inventors
- 👤 M Palombari
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 12:20
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/02; H04J3/06; H04J3/0635; H04J3/0685; H04J3/0688; H04J3/14
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
445 words
In a telecommunication system including a main terminal, a remote terminal, a signal path interconnecting said terminals for two-way transmission of pulse-code-modulated messages thereover with a predetermined basic pulse cadence, first coding means at said main terminal for the transmission of messages to said remote terminal over an outgoing branch of said path, first decoding means at said main terminal for the reception of messages from said remote terminal over an incoming branch of said path, second coding means at said remote terminal for the transmission of messages to said main terminal over said incoming branch, and second decoding means at said remote terminal for the reception of messages from said main terminal over said outgoing branch, the combination therewith of: a master clock at said main terminal normally emitting a continuous train of locally generating pulses timing the operation of said first coding means; discriminator means at said main terminal connected to said master clock for monitoring the operation thereof and emitting a consent signal under normal conditions; first extractor means at said main terminal connected to said incoming branch for determining the basic pulse cadence of messages received thereover from said remote terminal and for generating therefrom a train of substitute clock pulses; first switch means at said main terminal controlled by said discriminator means for normally directly said locally generated pulses to said first coding means and for replacing said locally generated pulses by said substitute clock pulses to control the operation of said first coding means in the absence of said consent signal; circuit means connecting said discriminator means to said first coding means for inserting a recurrent verification code in a message transmitted to said remote terminal in the presence of said consent signal; a normally blocked standby clock at said remote terminal operable in a rhythm approximating that of said mater clock; detector means at said remote terminal connected to said decoding means for determining the presence of said verification code in a message received from said main terminal; second extractor means at said remote terminal connected to said outgoing branch for determining the basic pulse cadence of messages received thereover from said main terminal and for generating therefrom a replica of said locally generated pulses; and second switch means at said remote terminal responsive to said detector means for normally directing the pulses generated by said second extractor means to said second coding means for controlling the operation thereof, said second switch means being effective in the absence of said verification code to unblock said standby clock and to substitute the output thereof for the pulses generated by said second extractor means to control said second coding means.
Claim 2
Dependent Claim
445 words
In a telecommunication system including a main terminal, a remote terminal, a signal path interconnecting said terminals for two-way transmission of pulse-code-modulated messages thereover with a predetermined basic pulse cadence, first coding means at said main terminal for the transmission of messages to said remote terminal over an outgoing branch of said path, first decoding means at said main terminal for the reception of messages from said remote terminal over an incoming branch of said path, second coding means at said remote terminal for the transmission of messages to said main terminal over said incoming branch, and second decoding means at said remote terminal for the reception of messages from said main terminal over said outgoing branch, the combination therewith of: a master clock at said main terminal normally emitting a continuous train of locally generating pulses timing the operation of said first coding means; discriminator means at said main terminal connected to said master clock for monitoring the operation thereof and emitting a consent signal under normal conditions; first extractor means at said main terminal connected to said incoming branch for determining the basic pulse cadence of messages received thereover from said remote terminal and for generating therefrom a train of substitute clock pulses; first switch means at said main terminal controlled by said discriminator means for normally directly said locally generated pulses to said first coding means and for replacing said locally generated pulses by said substitute clock pulses to control the operation of said first coding means in the absence of said consent signal; circuit means connecting said discriminator means to said first coding means for inserting a recurrent verification code in a message transmitted to said remote terminal in the presence of said consent signal; a normally blocked standby clock at said remote terminal operable in a rhythm approximating that of said mater clock; detector means at said remote terminal connected to said decoding means for determining the presence of said verification code in a message received from said main terminal; second extractor means at said remote terminal connected to said outgoing branch for determining the basic pulse cadence of messages received thereover from said main terminal and for generating therefrom a replica of said locally generated pulses; and second switch means at said remote terminal responsive to said detector means for normally directing the pulses generated by said second extractor means to said second coding means for controlling the operation thereof, said second switch means being effective in the absence of said verification code to unblock said standby clock and to substitute the output thereof for the pulses generated by said second extractor means to control said second coding means.
Claim 3
Dependent Claim
63 words
The combination defined in claim 1 wherein the connection between said second decoding means and said detector means comprises two leads respectively energized by message signals arriving at normal rate over said outgoing line and by said verification code accompanying said message signals, said second switch means being effective to unblock said standby clock upon de-energization of at least one of said leads.
Claim 4
Dependent Claim
24 words
The combination defined in claim 1 wherein said discriminator means comprises a resonant circuit tuned to a frequency corresponding to said predetermined pulse cadence.
Claim 5
Dependent Claim
46 words
The combination defined in claim 1, further comprising other discriminator means at said remote terminal connected to said standby clock and to said second coding means for inserting a verification code in a message transmitted to said main terminal upon proper orientation of said standby clock.
Claim 6
Dependent Claim
37 words
The combination defined in claim 1 wherein said first and second coding means are generators of bipolar message signals, said first and second extractor means including rectifiers for converting said bipolar message signals into unipolar pulse sequences.
Claim 7
Dependent Claim
61 words
The combination defined in claim 1 wherein said terminals are the junctions of respective groups of local lines, said first and second coding means including multiplexers for synthesizing a composite message from individual messages received from the associated local lines, said first and second decoding means including demultiplexers for directing responsive constituents of said composite message to the associated local lines.
Claim 8
Dependent Claim
43 words
The combination defined in claim 6 wherein each composite message comprises a recurrent frame divided into a plurality of channels of several time slots each, assigned to respective local lines, and a service channel containing said verification code in a time slot thereof.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-02 | 1976-10-02 | 1977-04-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-02 | 1980-10-02 | 1981-04-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-02 | 1984-10-02 | 1985-04-03 | $7700.00 | Window Closed / Lapsed |