This circuit is from a 1975 RCA tube manual. It appears elsewhere on the site. R5 depends on the voltage of the amplifier with which it is used and can be changed.
Passaje Alarm This locking circuit was found in a 1988 publication. It locks a relay when the...
Found in a publication for radio amateurs from the 1980s, this circuit amplifies signals in the 60...
We found this circuit in an application note from Linear Technology of the 90s. The circuit uses...