This circuit is from a 1966 publication. The frequency depends on the capacitors and on R1 which can have values between 47k and 2.2 M typically. The supply voltage can be between 200 and 300 V.
The sensor of this circuit is an NTC and the indication is made on a common analog indicator, and...
This 1.2 to 32 V x 3 A regulator was found in an 80's EDN. The power components must be equipped...
This circuit turns off after a time that depends on C1. The circuit is from an Electronics Now...