Circuit for remote supply of subscriber line terminals in a tele

Details Circuit for remote supply of subscriber line terminals in a tele Circuit for remote supply of subscriber line terminals in a tele

1986-04-10

1989-02-07

Ng, Jin F.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379387, 363 20, H04M 1900

Patent

active

048037222

ABSTRACT:
A circuit for remote supply of subscriber line terminals in telecommunication systems, especially suitable for employment in digital telecommunication systems, is described. The circuit comprises a supply circuit (10) at the beginning of the subscriber line (11), which circuit has a negative internal resistance operative when a preassigned supply amperage is exceeded. Between the subscriber line (1) and the terminal, a current converter cirucit (12) is provided, containing an energy reservoir (40) on the primary side and a switch-on circuit (41-44) operating in dependence upon its charge voltage for the switch pulses required for start-up. The operating current for the switch pulses is then delivered by a secondary winding (57) of the converter transmitter (27). A pulse width modulation of the switch pulses is effected, in addition to a control voltage derived from the secondary side of the converter transmitter (27), in the switch-on process, by a rising ramp-like direct current voltage preventing too violent a discharge of the condenser (40) at the input of the current converter (12). When switched on, the entire arrangement brings about a slow rise of the current on the subscriber line (11). Furthermore, the condenser meets the exaggerated energy demand upon start-up of the current converter (12) and compensates for fluctuations in energy demand during operation. The switch-on circuit (41-44) is kept switched on after the current converter (12) has been switched on by way of a direct current voltage derived form the secondary side, even if the input voltage drops below the switch-on circuit (41-44) switch threshold operative in the switched-off condition.

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"Resonant Switching Converter", B. E. Patterson, IBM Technical Disclosure Bulletin, vol. 22, No. 8B, Jan. 1980, pp. 3551-3552.
"Local-Battery Cahrging Over Subscribers' Lines", B. R. Freer et al., The Post Office Electrical Engineers' Journal, vol. 66, Part 2, 1973, pp. 73-76.

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