This circuit with TTL output was found in a 1968 EEE. The transistor can be of general use. The tunnel diode is an uncommon component today.
The LDO series (Low Dropout) TPS80 from Texas Instruments (www.ti.com) can provide output voltages...
Suggested by an American publication, this circuit has 5 operating conditions indicated in the...
Found in a documentation from the 70s, this circuit can be implemented today with ease. The relay...