ATX power switch substitute

If you install an AT motherboard with both ATX and AT power supply connections, in combination with an ATX power supply, in an AT enclosure, this circuit will save you from also having to install an additional pushbutton switch.An additional pushbutton switch is normally required for the ATX Power Switch/Soft Power Switch signal, but you can do without it if you use this simple circuit. It is an artful design, but it has been repeatedly tested. The zener diode is intended to provide protection against excessive voltages and reverse-polarity connection. In the latter case, the resulting short-circuit current (approximately 1 A) will exceed the allowable limit and cause the ATX power supply to shut down after around five seconds.