Panasonic KX-T7456 - Digital 24 Button Speakerphone Display, Specifications

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The data communication circuit serves the following functions:
Information exchanger between the DSHS and DSHS proprietary telephone, key input
information as well as data for the LED control, LCD control, etc. This information is
continuously exchanged at all times.
2) Circuit Operation
When the DSHS propritary telephone receives an IRQ signal from the DSHS and after sending
the key input information to the DSHS and receiving data for the LED control, etc., the DSHS
proprietary telephone will return to the DSHS an acknowledge signal.
3) Reception
The data from the DSHS is received via the H and L lines along the path shown below.
H, L Line T1 IC11 Pin 5, 10 IC1 Pin 38, 39 IC1 Pin 21 IC2 Pin 22 (IC5 Pin 8)
4) Transmission
The data to the DSHS proprietary telephone is transmitted along the following path.
IC2 Pin 23 (IC5 Pin 13) IC1 Pin 20 (IC1 Pin 19) IC1 Pin 40, 41 Q1, Q2 T1 H, L Line
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