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

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value is 255.
7.8. HOOK SWITCH CIRCUIT
1) Circuit Operation
The hook switch of this unit employs the photo switch consisting of LED and photo transistor.
The 2kHz pulse from the gate array of IC2 causes the LED to emit the light. The light is
interrupted at ON-HOOK and passes through at OFF-HOOK by the hooking bar,so that the
hooking is performed controlling the light of the photo transistor. The detection signal is
determined by the microcomputer of IC6.
7.9. HANDSET CIRCUIT
1) Transmission signal path
The analog input signal from the handset microphone is input to the communication LSI
through the IC2 built-in analog amplifier. In this LSI the network control based on A/D
conversion and the handset software and the gain control based on the down load data from the
PBX are performed. The voice data is sent to IC1 by the serial transmission. The voice data is
transmitted between PBX and DPITS with the protocol originated by KME.
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