| 摘要 |
1530089 Telephone line circuits; hybrid circuits THOMSON-CSF 31 Aug 1977 [3 Sept 1976] 36417/77 Headings H4K and H4R A line circuit for 2/4 wire conversion between a line L1, L2 and the transmitting E and receiving means R of an exchange (not shown) includes differential amplifiers A1, A2, A3 and power amplifiers A4, A5 having biasing inputs, for connecting E to the two wires L1, L2, a differential amplifier A6 which through another differential amplifier A7 connects the line L1, L2 to R. A7 is also connected to E so that signals from E to L1, L2 are not retransmitted on R. A common unit (not shown) controls the operation of the line circuit through FET switches S1-S7 so that the circuit provides line feed, ringing, reversing polarity of the line, compensation for differences in line impedances and loop detection. The line circuit may be formed as an IC. |
