This circuit was obtained from Motorola documentation. It generates light pulses at a rate of 120 per minute. Equivalent transistors can be used. The circuit can also excite high brightness LEDs.
The transistors are 2N918, 2N3464 and other RF equivalents of the time for Q1. For Q2, 2N3399, 2N2894...
This circuit, which can be used as a shield, was found in a 90s Electronic Design. The circuit...
This interesting intercom circuit was obtained from an Argentine publication from the 1970s....