| 摘要 |
Echo propagation is prevented on four-wire signaling path to two-wire signaling path connections. A first transmission path portion is extended from the receive leg of the four-wire signaling path to the transmit leg and a second transmission path portion is extended from this point to the two-wire signaling path, the first and second transmission path portions thereby forming a bidirectional path carrying signals from the two-wire signaling path and from the receive leg. Detection circuitry is located in the first transmission path portion and develops a voltage signal which determines the direction of signal transmission between the four-wire and two-wire signaling paths. Echo propagation is prevented during signal transmission from the four-wire signaling path to the two-wire signaling path by opening the transmit leg of the four-wire signaling path. Echo propagation is prevented during signal transmission from the two-wire signaling path to the four-wire signaling path by closing the transmit leg and removing gain from the receive leg of the four-wire signaling path.
|
