[ARC5] R-23/ARC-5, MX-19/ARC-5 Instrument Landing System??

[Mike Morrow]

Has anyone got any details of the "instrument landing equipment" that the R-23 and the MX-19 audio adapter were designed to support?

I have an R-23 with said adapter, and the R-23 has the yellow dot above the tuning shaft connection that indicates that the ILS audio circuitry therein had been modified to provide more equal output of the 90 and 150 cps ILS audio tones.  The MX-19 was made under a different contract number than the R-23 was, and it has the old cotton/rubber insulation rather than the vinylite insulated wiring one usually expects on ARC-5 units.  It almost looks as if the system, whatever it was, may have been actually used somewhere.

According to the AN/ARC-5 maintenance handbook, the cable that connects to the front of the MX-19 has a connector only on one end, which seems strange.

It appears to me that, other than using 90 and 150 cps audio signals, this USN ILS must have differed substantially from the USAAF's RC-103 (BC-733) and AN/ARN-5 ILS combo.

If this USN ILS never actually saw the light of day, I wonder why even the late R-23A receivers had circuitry to support it?  Also, would anyone have an estimate of when the R-23A made its appearance?  Was it in service before WWII ended?

Thanks,

Mike / KK5F