A3.8 Telu Circuit Diagram (Option) - Oki OKIOFFICE44 Service Manual

A3.8 TELU Circuit Diagram (Option)
The TEL U Board is used for control of the telephone set when the optional telephone assembly is
installed on the facsimile transceiver,
1. Block diagram
• Figure A3.8.1 shows a block diagram of TELU circuit.
2. General functions of this circuit are as follows:
• Speech IC
• Sending Level Adjustment
• Receiving Level Adjustment
• Sending Frequency Response Adjustment
• Side Tone Adjustment
• DC V-1 Characteristics Adjustment
• Return Loss Adjustment
• AGC (automatic gain control)
• Manual Pad
• Sending Frequency Response Adjustment
• Receiving Frequency Response Adjustment
• Handset Interface
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
Board Descriptions
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.
A - 54 OKIOFFICE 44 Serv. Man., P/N 59276801