[ARC5] AN/APX-1 and AN/APX-2 IFF systems

[Andy Young]

Can somebody clarify for me, please, the differences between the AN/APX-1 and AN/APX-2 IFF systems?

I am confused because I have a receiver/transmitter unit with two ID plates. The one on the upper chassis reads TN-8/APX-1, and the one on the lower chassis reads RT-24/APX-2.

I can find reference to RT-24/APX-2 on the internet, but not to TN-8/APX-1.

What exactly have I got?

Many thanks,

Andy