Oki B 4100 Maintenance Manual page 459

3. Explanation of TEL circuit diagram
This section describes functional blocks of individual TEL circuit diagram.
3-1 TELU circuit diagram
TELU circuit diagram is formed by Speech IC and interface of UNC, HOOK SW and HANDSET.
1) Speech IC
The hybrid circuit is formed by Speech IC.
2) Handset Interface
• Transmitter signal route
• Receive signal route
40055101TH Rev.4
Signal from the microphone of the handset is input to pin 15 and 16 of Speech IC. This
signal is determined by the amplification factor and output to the telephone line via
UNC, Hook switch and DB2 (rectifier).
Receive signal from the telephone line enters Speech IC via UNC, Hook switch and
DB2 and is output to pin 2 & 3 of the speaker of the handset.
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