Reset Circuit; Door S/W Sensor Circuit - Samsung RT40MA Service Manual

3. Reset Circuit

The reset circuit makes all program functions operate at the
initial stage by initializes the various parts such as RAM in
MICOM when the power is supplied or the power is supplied
to the MICOM power by a power failure in a moment.
When the power is supplied, the voltage of reset becomes
low during scores of uSEC, and it maintains high during the
normal operation.

4. Door S/W Sensor Circuit

If door is open, R-DOOR S/W contact is closed. Then when RED LINE supplies power to GRAY
LINE passing through R704 and PHOTO COUPLER(PC817) LED and D702, PC817 operates
and generates 50 or 60HZ globe-shaped wave.
MICOM recognizes this waveform and detects that door is open.
If door is closed, R-DOOR S/W contact is open and power is not supplied to PC817, MICOM
recognizes that door is closed as DC5V is maintained continuously.
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