Indicated for powering circuits with operational amplifiers, this source was found in Popular Electronics. The output voltage depends on the transformer used, as well as the current.
This circuit of a 1978 American publication monitors a telephone line by triggering a relay. The...
This interesting FET-tester circuit was obtained from an old American documentation. The bipolar...
This old VHF TV booster that also serves FM was found in Radio Electronics magazine from April...