Panasonic DX-600, Service Manual

Page: 221 / 358

221
DX-600/800
APR 2002
Edition 1.0
Dial Pulse Generator
The Dial Pulse Generator consists of a CML relay, a DC hold circuit, a dial pulse generate circuit and their
peripheral circuits. The generator generates dial pulses. The CPU on the SC PC Board controls all dial
pulse generation sequences. When the absence of the terminating message is confirmed by the Off-Hook
detector in DAA (IC23), the CPU turns the CML relay ON and the dial pulse generate circuit ON through
DAA to develop loop status (DC loop). After a few seconds, the CPU turns the PLS relay ON and OFF to
generate dial pulses, making and breaking the loop. The line status during dialing is shown below.
DTMF Tone Generator
The DTMF Tone Generator is incorporated in the MODEM on the SC PC Board. The DTMF tone is
conveyed to the telephone line using the same route as the facsimile signal. The DTMF tone selection is
controlled by the CPU. Digital amplitude signal is conveyed as analog amplitude signal through D/A
converter in the DAA (IC23). The line status during dialing is shown below.
Ring Detector
When the unit is in the Sleep Mode status, a Ringing signal is detected by a photo-coupler (PC2) in Ring
Detector to cancel the power-save for waking up. Then DAA (IC23) detects the ringing signal for receive
mode.
When the unit is normal operating status, DAA (IC23) detects the ringing signal immediately.
CML Relay
Dial Pulse
Generate Circuit
Line status
break
make
make
break
Line release
Speech
condition
First
digit
make
break Prepause
Inter-digit
pause
Speech
condition
Speech
condition
Second
digit
CML Relay
Line status
break
make
Line release
Speech
condition
First
digit
make
break
DTMF signal
Signal time
Inter-digit
pause
Speech
condition
Second
digit
Speech
condition