This is one of first low power transmitters for amateur band. This is "pair of 45's in push- pull" oscillator rig.
Left side has adjustable coil going to 50 K resistor. Left square wave source input is where telegraph key (open switch) is located. 500 pf capacitor is adjustable and tapped coil going to upper right transmitter antenna. #45 tube filaments are 2.5 volts at 1.5 amp. Maximum plate voltage is 275 volts.
