The Wireless Set no 38 AFV was used in conjunction with the Wireless Set no 19 in Armoured Fighting Vehicles, like tanks. For instance the British STUART tank.
At the controll units, no 16 and 17, connected to the WS 38 with low frequency amplifier part and the WS no 19, you could make a choice between the WS no 19 , WS no 38 or intercommunication amplifier. This intercommunication amplifier, was used for communication between the members inside the tank. Also to increase the audio strenght of the WS no 38 receiver part. The amplifier was needed, because of the heavy noise in the tank itselves.
At the right the transmitter/receiver WS no 38 AFV and at the left the intercommunication low frequency amplifier.