KX-TDA100DUP - Panasonic PBX Service Manual (repair manual). Page 15

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• DPT data communications

Bch/Dch/Cch data is transmitted from the DTL/DTH terminal of ASIC, and the AMI-converted pulse signal is output to DPT
(between D1 and D2) by way of the driver U403 and the pulse transformer T400. The Bch/Dch/Cch data transmitted from DPT is
input to the DR terminal of ASIC by way of the pulse transformer T400 and R411. ASIC compares VREF+ and VREF- with the
input waveform, and receives a valid pulse.
Do the same for the 2nd to 4th ports (circuit numbers 500-599, 600-699, 700-799) 

• Bch communications

Communicated by the PCM data (64kbps x 2) connected from the local highway by ASIC.
Used mainly for the audio signal of DPT.

• Dch communications

Communicated by the data (16kbps) protocol-converted by the HDLC controller in ASIC.
Used mainly for the control signal of DPT.

• Cch communications

Communicated by the data (8kbps) converted by the serial/parallel-converting circuit in ASIC.
Used mainly for recognizing the terminal model.

• PT current-supply circuit

+40V is superimposed on the transmit/receive data line (D1, D2), and fed to PT. Supply voltage is and +40V for new DPT. It will
be switched after the connected PT is judged through communications. I/O control is as follows.