We found this balanced modulator circuit for DSB and possibly SSB transmissions in US 1980s telecommunications documentation. The diodes can be replaced with equivalents.
This shield circuit for PC was found in an English documentation from 1996. The current of the...
When any of the sensors is interrupted, the relay closes its contacts and locks, not turning off...
This circuit using a general-purpose transistor was found in the July 1993 issue of Electronics Now...