This circuit was found in a 90s Popular Electronics. The circuit uses several relays in order to obtain different controls for power loads.
Equivalents of the same series as the LM239 and LM339 can be used in this application. The pulse...
This defrost alarm starts from an interesting idea. A small magnet on an ice stone is trapped at the...
This sensitive photo-relay can be mounted with modern transistors such as BC558 and with the...