This 8-tube amplifier with 12 W output was found in an American publication from 1947. The output is in counterphase with pentode tubes.
This circuit, from 1999 documentation, prevents the powered device from receiving power when it...
This circuit is intended for monitoring an environment. It fires a relay with a sound, but only if...
Found in a Popular Electronics from the 90's, this circuit uses integrated from that time, today...