Test Set I-209-B is a portable unit used in testing power supply systems of radio direction finders, radio intercept centrals, and any other equipment within its voltage and frequency ranges. It consists of a vibrating reed-type frequency meter and a dynamometer-type voltmeter.
- TM 11-2501 Test Set I-209-A. War Dept. Oct. 1943. 8 p. U408.3.A13 TM 11-2501 Oct. 1943,