DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the Figure, a telephone system, such as a private branch exchange ("PBX") 10 is schematically illustrated.
The PBX 10 includes a diplexer 12 which splits incoming composite voice/data signals from an electronic telephone into a voice signal and a data signal.
Diplexer 12 also acts as a bandpass filter which has a center frequency of about 32 kHz and a bandwidth of about 8 kHz.
The PBX 10 also contains an analog gate 14, a demodulator 16, a bandpass filter 18, and a data recovery and automatic gain control circuit 20.
The demodulator 16 demodulates incoming data signals and a modulator 22 modulates outgoing data signals.
A multiplexer 24 is connected to the demodulator 16 and a demultiplexer 26 is connected to the modulator 22.
The multiplexers 24, 26 are connected between the demodulator 16, modulator 22 and other PBX switching and control circuitry 28.
As illustrated, an incoming data signal comes through diplexer 12, analog gate 14, bandpass filter 18, demodulator 16 and to multiplexer 24.
On the other hand, an outgoing data signal comes through demultiplexer 26 and is modulated by the modulator 22 prior to being output to the diplexer 12.
The diplexer 12, data recovery circuit 20, modulator 22, multiplexers 24, 26 and the PBX control circuitry 28 are more fully described in copending application Ser.
No.
804,276 which is incorporated herein by reference.
As illustrated, there is one modulator 22 and one demodulator 16 associated with each diplexer 12, and consequently, with each electronic telephone.
Each multiplexer 24, 26 can accommodate eight circuits, and as arranged, multiplexer 24 is connected to eight demodulators 16 while demultiplexer 26 is connected to eight modulators 22.
By this construction, incoming data from an electronic telephone is demodulated prior to being multiplexed and outgoing data to an electronic telephone is demultiplexed prior to being modulated.
The gate 14 has its input connected to the output of diplexer 12 so that a data signal periodically enters the gate 14
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Multiplexer-related 
