British Thomson Houston BTH Vario Coupler Unit

British Thomson Houston (BTH)
Vario Coupler Unit

British Thomson Houston Vario Coupler UnitPlug-in vario-coupler for use in the BTH VR2 Form BA and Form BB valve receivers. Underneath it has a 4-pin valve base configuration. There is also a vario-coupler that covers the 1500-1800 metres band.