This telephone circuit was found on a 90's EDN. It keeps a flashing LED to indicate that there was a call in your absence. The components admit equivalents.
Found in Philips' 1967 documentation, this circuit makes use of period components. The SCR can be...
The LM143 is a high voltage operational amplifier not very easy to obtain today. The transistors used are...
Found in American documentation from the 90s, this circuit uses TTL technology and is therefore...