| 摘要 |
To match the AC-coupled exchange line to the terminal of a switching network with single-conductor switching, an arrangement make up of operational amplifiers is used, in which an operational amplifier (OP2), the output end of which is connected to the exchange line section at the branch exchange end via a transistor (TR), is in each case only controlled by voice signals coming from the switching network. The signal is picked up across a voltage divider, which is also formed by a balancing resistor, and conducted via the line transformer (LÜ) which is used for DC isolation, to the exchange line (AL). A simple arrangement (TR, R8, R9) ensures that audio frequency signals from the switching network do not reach the receiving branch. This is only possible for signals which are received via the exchange line (AL). For such signals, a reaction to the exchange line is impossible due to the effect of the operational amplifier (OP3) which is located in the actual transmitting path. <IMAGE>
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