Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – Including fault responsive disconnection of tested component
Patent
1995-02-24
1997-07-22
Kuntz, Curtis
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
Including fault responsive disconnection of tested component
379 27, 379 29, 379 30, H04M 124, H04M 308, H04M 322
Patent
active
056510489
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to communications circuits, and especially to maintenance termination units for use in telephone circuits.
In recent years, and especially in view of deregulation of many telephone systems, privately owned communication equipment has increasingly been installed in the premises of subscribers to the system, with the result that it is often necessary to determine whether any fault is located in the telephone line, or in the subscriber's premises, ie in the subscriber's equipment or cabling, in order to determine whose responsibility it is to repair the fault. It is highly advantageous economically if this determination can be performed remotely by sending an appropriate signal from the local exchange along the line, thereby obviating the necessity to send any telephone company personnel to the subscriber's premises.
In order to test the telephone line for any faults it is necessary firstly to install a so-called "maintenance termination unit" or MTU in the line at the subscriber's premises which can disconnect the subscriber equipment from the line (often called sectionalizing the line) and connect the A and B or tip and ring lines on receipt of the appropriate signals from the exchange. During the line testing procedure determinations will typically be made of the line to line resistance and of the first and second line to ground resistance. Also the line continuity can be determined by detecting the presence of the MTU electronically.
Various forms of MTU are described, for example, in U.S. Pat. No. 4,710,949 to Om Ahuja. This device comprises a pair of voltage sensitive switches, one located in each of the tip and ring lines, and a distinctive termination connecting the tip and ring lines on the subscriber side of the voltage-sensitive switches. The voltage-sensitive switches may each have a threshold voltage of about 16 volts so that they are closed in normal operation by the 48 volt battery voltage but will open when this is replaced by a test voltage below about 32 volts removed in order to test the line-to-ground and tip-to-ring impedances. The distinctive termination may, for example, comprise a back-to-back diode and Zener diode which will exhibit an asymmetric resistance when large voltages (higher than the operating voltages) of different polarity are applied. Other forms of MTU have been proposed in which the switches can be actuated by signals other than d.c. signals of one frequency and send back signals of another frequency.
Generally however, these MTUs suffer from the disadvantage that the control circuitry for operating the switches etc. allows a small leakage current to occur between the two lines when the testing is performed with the result that inaccuracies can occur in the determination of the insulation resistance of the telephone line.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a switching arrangement that can be connected in a communications channel that comprises a pair of lines, between sets of terminal equipment, which comprises: reservoir and controls the charging of the reservoir in response to a signal on the line; and line and will allow the reservoir when charged to energise control terminals of the line switches time by discharging of the reservoir.
The arrangement according to the present invention has the advantage that it can be connected in a communications channel such as a telephone line so that the control circuit for the line switches is on the subscriber side of line switches, and accordingly it is possible to have no circuitry connecting the lines on the exchange side of the line switches. Thus, when the line switches are opened during a test, the line-to-line resistance of the channel is a correct indication of the channel's insulation resistance. Clearly the control circuit is isolated from the exchange by the line switches during the test and so cannot be accessed from the exchange or receive power from the line. According to the invention the line switches are powered by
REFERENCES:
patent: 4143250 (1979-03-01), Simokat
patent: 4169220 (1979-09-01), Fields
patent: 4558182 (1985-12-01), Perry et al.
patent: 4653084 (1987-03-01), Ahuja
patent: 4807277 (1989-02-01), Perry
patent: 4852145 (1989-07-01), Bevers et al.
patent: 4862491 (1989-08-01), La Salle et al.
patent: 5345496 (1994-09-01), Galpin
Bertram Bruce M.
Burkard Herbert G.
Kuntz Curtis
Loomis Paul
N.V. Raychem S.A.
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