EMIS/ EFIS Alert Wiring Part II

[N178EZ]

Another easy one. If I wire the alert tone output wires from both the EFIS & the EMIS to the same channel on the intercom (Y together), do I need to diode protect each of them? The same question if I add a third (GPS) alert signal to the same input to the intercom. I obviously will have to do some testing with impedence matching between the GPS and EMIS. Do I need the same on the EFIS/ EMIS.

Matt

 

[dynonsupport]

The EFIS and EMS can be wired together with no resistors or diodes. A diode is actually a bad idea- these are AC signals so a diode will chop half of them off. Usually you need to add a resistor in-line to protect stuff. 1K on each line is the generic value for audio signals.