R1 may be 10k and R2 100k. The transistor can be the BC548 and instead of the small lamp we can use a series LED with a 1k resistor. D1 is germanium and C1 is 10 nF. C2 can be 47 nF.
This circuit checks the infrared emission of a common remote control. We found it in the March 1993...
This signal injector is of great use in the troubleshooting of radio receivers and amplifiers. What we...
Found in Popular Electronics from the 90s, this circuit generates two tones that are selected by a...