This wired intercom circuit was found in an English publication from the 80's. The integrated circuit can be replaced by an equivalent, just like the transistor which is a general-purpose type.
This 12 V incandescent lamp switch with time delay can be found in old documentation. The SCR can...
With this circuit it is possible to control the frequency of a 555 astable, given by C1 and R1...
This conventional astable uses two NPN transistor and was found in a publication of the year 1968. The...