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ASIC... IC1

• PLL circuit

Generates a multiply clock that is multiplied from 2.048MHz to 10.24MHz by IC701, IC702 and IC703, and uses it as a DNIC
(IC1A~D) clock.

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Bch PCM data is transmitted via the gain control block and the local highway I/F in ASIC (IC1) following the echo canceller
(IC706)

→CSMG2 [Including ADPCM transcoder function] (IC104, IC204)→DNIC (IC1A~D) (same as the reverse bus).

CHS4 is generated by the timing generator in ASIC. 

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It multiplies +40V on the transmission line (D1, D2) and supplies power from the power supply line (POWH, POWL). For +40V
short protection, it is configured with the PTC-thermistor TH1, power feeding switch Q1.
The feeding root is as follows.
+40V

→TH1→L2→CS and +40V→TH1→T1→L1→CS

CS

→L2→Q1→R13,R14→PG and CS→L1→T1→Q1→R13,R14→PG (0V)

• DC/DC conversion circuit

The circuit which generates output +3.3V, +5V with input +15V. It is configured with the circuit that reduces the voltage from +15V
to +3.3V by IC801, Q801 and L801 switching power supply, and with the circuit that reduces the voltage from +15V to +5V by
IC802, Q802 and L802 switching power supply.
There are some protection lines. 
The protection circuit consists of an output short protection and an overvoltage protection.
When an output of power supply is short, IC801 or IC802 works to stop the output as the output short protection.
When +5V and/or +3V output become overvoltage caused by Q801 and/or Q802 short, it is detected by D812 and D811. 
Q808 is cut by Q809 to shut down the input power supply as overvoltage protection.

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- Power Supply System
- It provides four power systems; +15V and +40V power input and +5V, +3.3V, +2.5V, +1.2V, +1.8V and +40V power output.