This circuit allows an SPST momentary pushbutton to act as a push-on push-off switch, using a DPDT latching (bi-stable) relay. It was originally intended to allow a single pushbutton switch on the ...
Figure 1a shows a latching circuit based on an optocoupler, IC 1. If the off switch remains closed, pressing the on switch powers the LED in the optocoupler. Thus, the transistor in IC 1 turns on. You ...