| 摘要 |
A two to four wire hybrid converter for use in a telephone system that allows other telephone equipment, such as a caller identification device, to more readily decipher signals. The converter controls noise by using a digital to analog converter, hybrid circuit, interface circuit, and controller. The digital to analog converter accepts a receive digital data signal from a transmission line and converts it to a receive analog signal. The hybrid circuit accepts the receive analog signal and provides it to the customer telephone line, as well as accepting a transmit telephone analog signal from the customer telephone line. Such transmit telephone analog signals are then converted to digital signals and provided to the carrier transmission lines. The hybrid circuit includes an inverter, variable amplifiers, and summing circuit. The inverter inverts the transmit telephone analog signal with respect to the receive analog signal. In the preferred embodiment, the summing circuit combines the inverted transmit and receive analog signals. A transmit variable amplifier changes the magnitude of the transmit analog signal provided to the summing circuit. A receive variable amplifier changes the magnitude of the analog signal provided to the customer telephone line. A trans-hybrid variable amplifier changes the magnitude of the receive analog signal to be combined with the inverted transmit analog signal. The controller detects whether or not the telephone has gone off hook. Upon receiving a signal that the telephone has gone off hook, the controller changes the gain of the variable amplifiers.
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