The power supply for this analogue circuit
that affords delays of 330 seconds is
taken directly from the mains. The direct
voltage at the output of the bndge rectifier
is held at 22 V by zener diode D5-Resistor
R6, which enables C, to discharge rapidly as
soon as the mains is switched off must be
rated at 250 V a.c. or 400 V d.c.
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