Hi All,
Just looking for some advice on what is probably a trivial issue. I've got a GMA340 audio panel, wired up with an IFD540 as COM1 and a KY97A as COM2. Currently it's wired exactly as shown in the GMA340 manual, which runs the COM KEY lines in shielded 2-core wires along with the corresponding COM MIC line. This is somewhat annoying as I need to bring a wire from COM 1 KEY down to the KY97A for the XMIT_REC_INTERLOCK (ie to stop it trying to receive when the IFD540 is transmitting), and I can't get to that wire because it's inside the shield...
The newer GMA345 manual doesn't shield the COM KEY lines at all. That makes sense to me; after all the KEY lines should just be very low-speed digital signals, largely immune to noise. Implementing that on the GMA340 would wiring up the KY97A interlock much easier...
GMA340 manual:
GMA345 manual:
So, thoughts from the community and/or Garmin? The options I can see are:
1. Follow the GMA345 manual, do a 1:2 splice on the now-unshielded COM 1 KEY line so it can connect to both the IFD540 (COM KEY) and KY97A (XMIT_REC_INTERLOCK). Easiest option all round.
2. Follow the GMA340 manual, splice on an unshielded wire at one end (where the COM 1 KEY line is accessible) and run that to the KY97A. I'm not fond of this as it would mean that there's now the potential for noise to get inside the shield and therefore into the COM 1 MIC line.
3. Follow the GMA340 manual, splice on a shielded wire at one end, tie the shields together. This seems like the safest option, but probably excessive.
Any further ideas?