KX170B glideslpoe

I have a KX170B with a faulty coms. I sent it to Honeywell and they sent it
back saying unserviceable. So I bought a used one off ebay and it works
really well. My question is regarding the Glideslope. I have a glideslope
in my original radio but the new one does not. I opened both units up to
compare and they look identical, no "extra" little circuit card in the
original for the GS function. So my questions:
- Is the GS function in the radio or in the head?
- If the GS is in the head, is there any changes/adjustments in the radio
for the GS, as my GS used to work in the original radio.

Thanks,
Ken