Panasonic DP-3000 Technical Manual page 24

Dial Pulse Generator
The circuit consists of the CML relay, PLS relay and their peripheral circuits. This circuit generates dial
pulses. The CPU on the SC PC Board controls all dial pulse generation sequences. It turns relay CML
and PLS ON and OFF through the DZZSP58025 (IC80). The status of the relays during dialing is shown
below. When the absence of the terminating message is confirmed by the Off-Hook detector, the CPU
turns CML relay ON 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.
Dial Pulse
CML Relay
PLS Relay
Line release
Line status
DTMF Tone Generator
The circuit is incorporated in the MODEM on the SC PC Board. The DTMF tone is conveyed to the tele-
phone line using the same route as the facsimile signal. The DTMF tone selection is controlled by the
CPU. The relay status during dialing is shown below.
DTMF Tone
PLS Relay
CML Relay
Line release
Line status
break
make
break
make
Speech First
condition
break
Prepause
make
break
make
break
make
Speech First
condition digit
Prepause
break
make
Speech Second
digit condition
Inter-digit
pause
Speech Second
condition
Inter-digit
pause
24
Speech
digit condition
Speech
digit condition
DTMF signal