Wireless of the Week - week 18
 

The Power Supply Unit No. 5 is a portable power supply unit for Wireless sets No.18 and 38 (see weeks 17 and 10 respectively) used in place of dry cell batteries when supplies of batteries were limited, in circumstances such as cold or tropical climates and when patrolling away from base where sets would consume more batteries than the patrol could carry. Because the unit is powered by a crank, it could provide limitless power as long as there was a Tommy to crank it.

Almost the same configuration of an 18 set, the Power Supply Unit No.5 consists of a hand crank generator, a vibrator unit to provide LT and HT voltages, and wet cell acid batteries (recharged with the hand cranked generator) to store power for the set, all housed in a pressed metal case.

Dimensions and harness are identical to the 18 set of last week. Weigh was 25 lbs. A removable cover on the front gave access to the generator, vibrator unit and batteries. Connecting cables for both the No.18 and No.38 sets were stored inside the unit. The crank and metal plate with instructions was on the right and sockets for either No.18 or No.38 set on the left.

While a great alternative for wireless sets that ran down their batteries all too quickly, the hand cranking speed of 100 to 110 rpm, weight and noise made the Power Supply Unit No.5 somewhat unpopular.