Accumulator / battery operation
In the early days of radio heaters and plate batteries were almost the only usable voltage source in the field; in military thus, this situation remained the same for years to rund the equipment independant from mains power sources.
The old sets used accumulators for valve heating, usually high current and a voltage of 6.3 volts were used. Furthermore, the vlaves required different plate voltages, which could be delivered by anode or plate batteries, or care battery or mains operated converters.
Poprtable military equipment of the sixties mostly used heater batteries (1.5 volts as standard) and anode or plate batteries (special format, usually 51 or 103 volts).
The solid state sets from the seventies are battery operated and usually require standard battery types, with the exception of the widely used handheld Swiss „walkie-talkie“ SE-125 which requires a 7.5 volt battery; after these special batteries were out of stock, an adapter for use with standard UM3 / AA batteries has been developed.