Metal locator (CB7506E)

This simple metal detector was found in a 1960 Sylvania transistor manual. The phone must be high impedance or crystal.

LDR Sensitive Passage Sensor (CB24482E)
This circuit is more sensitive than the previous one, in the sense that we can use weaker and more...
100-second monostable (CB25671E)
This 3-transistor timer was found in the January 1994 issue of Electronics Now magazine. The...
Bistable with two 555 (CB1294E)
This circuit appears in other articles in this section, but it is very interesting. It is a...