The AIS 200B-35 is a 20-pole, signal level, switching unit designed for use with NAV systems that share the aircrafts HSI/CDIs OBS functions. The contact switching rating is limited by the circuit board track current capacity to 1.0 amp. This unit has a revisionary relay which selects the LOC signal for display on the HSI/CDI whenever a LOC channel is selected in the NAV unit. This unit uses 10 relays in a series/parallel arrangement to provide the same 20 poles of switching. While model AIS 200B-35 is a direct fit and replacement for the AIS 200-35 and AIS 200A-35 models, installation of this AIS 200B-35 remains the same. Operates on 28 VDC.