Panasonic UF-585 Service Manual page 201

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
SCA/SCB PC Board controls all dial pulse generation sequences. It turns relay CML and PLS ON and OFF through the
MN86075 [IC17] (UF-585: MN86074 [IC7]). 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
break
Line status
DTMF Tone Generator
The circuit is incorporated in the MODEM on the SCA/SCB 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. The relay status during dialing is
shown below.
DTMF Tone
PLS Relay
CML Relay
Line release
break
Line status
break
make
Dial pulses
break
make
First
Speech
condition digit
Prepause
make
break
make
break
make
Speech First
digit
condition
Prepause
make
Dial pulses
Speech Second
condition digit
Inter-digit
pause
Speech Second
condition digit
Inter-digit
pause
System Description
Speech
condition
Speech
condition
DTMF signal
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