Telephonic communications – Subscriber line or transmission line interface
Patent
1990-12-20
1994-03-08
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
379403, H04M 100
Patent
active
052934217
ABSTRACT:
Summing amplifiers may be constructed from feedback operational amplifiers. The weighting factors are quotients of the feedback resistance common to all quantities to be summed and the individual dropping resistances. Only the feedback resistance has a directly proportional effect, while the effects of the individual dropping resistances are inversely proportional. The formation of specified complex weighting factors is difficult, especially if the summing amplifier is intended for use in a two-wire/four-wire interface between a subscriber line and a telecommunications network and is to be mass produced at low cost as an integrated circuit. By means of a two-stage summing amplifier in which the second stage (VS2') sums with real factors, while complex factors are implemented in the first stage (VS1'), both balanced- and unbalanced-to-ground interfaces can be implemented in a simple manner with only one capacitance. Common-mode signals are simple to evaluate (SSE); common-mode signalling (DS) is possible.
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ALCATEL N.V.
Chiang Jack
Dwyer James L.
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