The ASI-223 Zifor III demodulates and extracts bearing information from a VOR audio signal generator and displays the zero radial information to an accuracy of ?0.01?. The ASI-223 also displays radial bearing run out error to within ?0.01? at any radial from 0.00 to 359.99?. Input signal status and automatic self-test information are also displayed. The ASI-223 Zifor III acts as a precise phase meter, measuring the phase relationship of the 30 Hz reference tone (which has been stripped from the 9960 Hz FM subcarrier) to the 30 Hz variable signal. The amplitude of the 30 Hz variable signal is also monitored to ensure that the input tones are within proper levels.

An RF Detector/Amplifier Module (ASI-22-3A1) is available as an option for testing VOR Signal Generators. The ASI-22-3A1 receives the RF input from a signal generator and filters out the VOR composite signals utilized by the ASI-223. The ASI-22-3A1 can be used externally on the bench or installed in the ASI-223,m 478A-3, or 78A-3.