Sharp A260 Service Manual - Page 38

UX-A260U [3] Circuit description of TEL/LIU PWB (1) TEL/LIU block operational description 1) Block diagram LINE CML H L CI DETECTOR PC2A TEL/LIU PWB IC101-A TXOUT RXIN IC101-B CONTROL PWB SIGTX SIGRX MODEM BLOCK (20438 I/A) SPKRP MICP LINEIN MIC ENABLE SP OUT ENABLE MIC /LINE SELECT RTLOOP 0,1 0,0 1,0 1,1 LPF RX TX HANDSET Q101 TEL MUTE (H:MUTE) MIC MUTE (H:MUTE) Q102 IC101-D TEL IN IC101-C SPEAKER IC7 SP MUTE (H:MUTE) Q105 LINE IN ENABLE 0,20,25,30dB Q104 IC5 +24VL DG SPOUT BZOUT1 LINE OUT DTMFMUTE RCVOL SP MUTE TEL MUTE CI CML MIC MUTE VOL-A VOL-B VOL-C LINE OUT ENABLE MUTE,0,-6,-12dB LINESEL 1,1 0,0 1,0 IC3 SCE214V FAX CONTROLLER Fig. 5 0,6dB DAC SIN ADC 0,+4dB SOUT 2) Circuit description The TEL/LIU PWB is composed of the following 6 blocks. 1. Speech circuit section 2. Dial transmission section 3. Speaker amplifier section 4. Ringer circuit section 5. CI detection circuit 6. Signal/DTMF transmission level & receiving level 3) Block description 1. Speech circuit section • The receiver volume is an electronic volume type, this model is switched in 3 steps. 2. Dial transmission section • D.P. transmission: The CML relay is turned on and off for control in the DP calling system. (Refer to the attached sheet.) • DTMF transmission: It is formed in the modem, and is output. 3. Speaker amplifier section • Ringer volume :It is controlled by the combination of the attenuator value of the LINE DRIVER in the modem and the ringer sending level sent from the modem. • Speaker volume :It is controlled by the attenuator value of the IC5 and IC3 (VOL-A,B,C) 4. Ringer circuit section • The ringer sound is formed in the tone of modem when CI signal is detected. The amplifier circuit drives the speaker of the main body. 5 - 10 manuals4you.com