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

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2) Reception signal path
The voice serial data transmitted from PBX is sent to IC1 or IC2 by the serial data. The network
control, gain control , A/D conversion is performed in IC2, then the data is output from the
handset speaker. Q31 of the handset speaker performs the mute operation by controlling IC6.
3) Corcuit diagram for transmission/reception signal path
Refer to page SCHEMATIC DIAGRAM ().
7.10. SP-PHONE CIRCUIT
1) Transmission signal path
The analog input signal from SP-phone microphone is input 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. IC3 is the SP-phone
amplifier, which turns ON/OFF using the port of IC2. The analog switch of IC12 interrupts the
input signal. Also the OHCA voice signal from the speakerphone IC1 of IC4 is output from the SP
-phone amplifier IC3.
2) Reception siganl path
The voice serial data transmitted from PBX is sent to IC2 by the serial transmission. Then the
signal is output from the handset speakerphone after performing the network control, gain
control, and A/D conversion in IC2. The SP-phone microphone has the mute function, which
interrupts the input signal with the analog switch and controls the port of IC2 with Q26.
3) Circuit diagram for transmission/reception signal path
Refer to page SCHEMATIC DIAGRAM ().
7.11. OHCA CIRCUIT
1) Circuit operation
In the OHCA mode, the voice serial data output from IC1 is converted to the analog signal
through IC5, then input to the SP-phone IC1 of IC4. The signal is input to the SP-phone amplifier
of IC3 and output from the speaker, resulting the OHCA operation with independent circuit
which is different from the voice transmission/reception circuit through the ordinay IC2
communication IC.
2) Circuit diagram for signal path
Refer to page SCHEMATIC DIAGRAM ().
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