Multiplex communications – Diagnostic testing – Using oam cells
Patent
1995-06-01
1997-05-13
Marcelo, Melvin
Multiplex communications
Diagnostic testing
Using oam cells
370521, 370524, 379 1, 379106, H04J 318, H04M 1106, H04M 1908
Patent
active
056299311
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to an information transmission system, in particular a telephone system, in which subscribers can be connected with a central office via a line, a bidirectional multiplexer and demultiplexer, respectively, being connected at the central office end and at the subscriber end of the line via a modem circuit which is likewise bidirectional and which modulates and demodulates data corresponding to the intended transmission, and in which a bidirectional compressor circuit and decompressor circuit are connected to the multiplexer and demultiplexer, respectively, to which the subscribers are connected, as the case may be, via a forward channel and reverse channel and at least one bidirectional analog-to-digital converter (CODEC), preferably a SLAC (bidirectional analog-to-digital converter (CODEC) with subscriber interface circuits (SLIC)), and to which switching equipment of the central office is connected via control circuits.
A system of this type is known from WO 91/20141. In such systems, problems arise in locating errors. In these systems, error diagnosis on the subscriber lines is restricted to very specific individual cases such as monitoring of ringing current thresholds, detection of short circuits and the like. In many cases, relays are used to connect at least preferred subscribers with the central office electrically in the event of errors. In all cases, conversion of telephone systems with direct connection of the subscriber to a central office line, e.g., via two-motion selectors, to the system mentioned above drastically limits maintenance and error diagnosis possibilities on the central office side.
The object of the present invention is to overcome these disadvantages and to provide an information transmission system of the type mentioned above which possesses good diagnostic possibilities.
According to the invention, this is achieved in that a measuring circuit, regulating circuit or control circuit is arranged between every subscriber (1) and the CODEC, SLIC or SLAC (2) associated with the subscriber or is at least partially integrated with the CODEC, SLIC or SLAC (2).
In this way it is possible to monitor the lines leading to the subscriber which could not previously be detected from the central office side in the information transmission systems mentioned above.
These measuring, regulating and control circuits which can be used for measurements and diagnostic functions and installed in an integrated subscriber circuit without great cost can detect leakage currents in the subscriber lines when the subscriber set is hung up, i.e., the leads relative to one another and to ground, the line resistance when the handset is off the hook, the ringing current and the impedance when the handset is hung up, the symmetry, differential voltages, differential currents, as well as the call charge pulses, synchronization current, the longitudinal alternating current, proper functioning of line safety elements and lightening protection elements and the ambient temperature.
According to a further feature, controllable switches are connected to the lines leading to the subscribers to enable a signal connection between the forward channel and the reverse channel of the same partial channel or, in multichannel solutions, e.g., of another partial channel.
In this way, it is possible, proceeding from the central office, to listen in to or speak on another connection for testing purposes while conversations are in progress, to follow voltage signals or current signals to different points of the transmission path or to effect stimulation at these points in a purposeful manner. The transmission of the corresponding values is made possible by the broad band of the voice channel and maintenance channel.
Further, a coupler connected to the forward channel and reverse channel, preferably a transformer with an isolating capacitor, can be arranged at the subscriber side of every SLAC and connected with the regulating circuit which is connected with a comparison circuit, e.g., a differential circuit,
REFERENCES:
NTG-Fachberichte, vol. 64: New Developments in Telecommunications, delivered at the NTG Conference of Apr. 17-19, 1978, pp. 64-68.
Feiereisen Henry M.
Marcelo Melvin
Semcotec Handelsgesellschaft m.b.H.
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