We have many tube tester circuits in this section. This one came out on a Radio Electronics from 1949 and has a very elaborate configuration with toggle switches.
This circuit, which can be used on an optical link, is suggested by the Texas Instruments...
This source, from a 1998 publication, can be used as a battery charger. The diodes are for 10 A x...
We found this circuit in an old publication on oscilloscopes. Its purpose is to observe the Ie /...