Telephonic communications – Diagnostic testing – malfunction indication – or electrical... – With blocking of normal usage
Patent
1996-04-19
1998-12-08
Kuntz, Curtis A.
Telephonic communications
Diagnostic testing, malfunction indication, or electrical...
With blocking of normal usage
379 1, 379 26, 379 29, 370249, H04M 124, H04M 308
Patent
active
058481273
ABSTRACT:
A two-wire channel unit or line card for use in a digital loop carrier (DLC) telephone system is disclosed. The channel unit is provided with a loopback test capability by using relays to open-circuit or short-circuit the input terminals of the hybrid circuit that couples the two-wire subscriber line to the separate two-wire transmit and receive paths within the channel unit. When open-circuited or short-circuited in this manner, the hybrid circuit couples voice frequency test signals between the receive and transmit paths of the channel unit, thereby allowing loopback testing to be carried out without providing a dedicated loss/gain circuit in the channel unit. An additional relay may be provided to vary the gain of an amplifier stage in the transmit or receive path of the channel unit during operation in the loopback test mode, in order to control the overall gain of the channel unit during loopback testing.
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Pulsecom Technical Manual, Practice Section 1306, "4-Wire, 600-Ohm Transmission Only Channel Unit with Loopback Model 4TOLB-3L1" (Doc. Issue 2, May 1992, pp. 1-11).
Pulsecom Technical Manual, Practice Section 1284, "2-Wire Transmission Only Channel Unit Model 2TO-1L2" (Doc. Issue 2, Jan. 1991, pp. 1-9).
Exar XR-T2713 Loopback Detector, pp. 2-138 through 2-140 (not dated).
Telecommunications Transmission Engineering, Third Edition, vol. 1, p. 678, (Bellcore, 1990).
Gadsby Winston M.
Levitan Dmitry
'Hubbell Incorporated
Barnie Rexford
Holmes John E.
Kuntz Curtis A.
Presson Jerry M.
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