The NT-11 Crystal Calibrator is a test oscillator used to tune accurately the A-set of Wireless Set No. 19. It may also be used with other sets. The unit was developed and produced in Canada and principally used in the Canadian Army. Officially it was not introduced for use in the British Army, who relied on the Wavemeter Class D No. 1. Electrically the Crystal Calibrator NT-11 is similar as used in the receiver unit of Canadian Wireless Sets No. 9 and No. 52. The installation kit included a Slow Motion drive which was intended to replace to original knob on a Wireless Set No. 19 Mk.II.
Inside view of Crystal Calibrator. Note that two spare valves are carried inside the unit. The crystal holder (vertical brown block in centre), is mounted just below the coil unit.
Fitting the Crystal Calibrator NT-11 on a Canadian Wireless Set No. 19 Mk.III. Note special 12-pt connector with supply lead for calibrator.