Found on a 1964 CQ this circuit is intended for tone frequency change modulation (FSK) telegraphic transmissions. It operates with signals of 2.975 and 2.125 Hz.
This circuit with power MOSFETs was found in a 1980s Siliconix documentation. Equivalent MOSFETs...
This 80's General Electric circuit is guarded by the noise-guard for operating current. The...
This circuit was obtained in a 1964 Electronic Design. The components used are from that time....