We found this circuit in the 1957 Raytheon transistor application manual. The transistor can be a BC558 and the common 6 V relay, just by using this voltage in the supply.
This circuit was found in an English magazine from 1973. The magazine no longer exists, but the...
This radio version of 1 transistor, extensively explored on this site and in this section, is from...
This dual control was based on Texas Instruments documentation for the CD4050. The circuit has two...