The circuit shown is for testing both signal diodes (low current) and rectifiers (high current). The circuit is from a 2000 Poptronics, and the transformer has a secondary winding of 100 to 300 mA.
The simple optical intercom we show is from a 1995 documentation. The LEDs can be infrared or...
With this circuit it is possible to monitor a signal that is being recorded on an old tape...
An oscillator that can be frequency controlled by a resistive sensor is shown in the figure. The...