"JFLEISC" wrote in message
...
I could use some wiring help here. I'm not that good at the terminology
but I
know that and always ask advice, so things usually turn out right.
Question; I'm wiring in a used DME and the ident (audio) output has a
choice of
'high impedance out' or 'low impedance out'. What's the difference? Is one
for
direct to headset and the other for going through the amp in the nav/comm
receiver or something like that? Thanks in advance.

Jim

Jim, in audio circles (where I kind of know what I'm doing; I usually only
lurk here in r.a.h), the output impedence of a device needs to be set
according to the input impedence of the device it's feeding. In simple
terms, the output impedence acts like a resistor in-line with the output.
Input impedence acts like a resistor tying the input to ground.

Output impedence: Input impedence:

device--resistor--output input-------device
|
|
resistor
|
|
ground

When you connect the two together, the two resistors (impedences) form a
voltage divider that decides how much of the signal is going to make it to
the next stage, and how much gets shunted to ground. In very general terms,
low output impedence coupled to high input impedence is desirable because
that means less of the signal is lost. For that reason, if I were hooking
up a sound system and was in doubt, I'd try the low impedence output setting
first. I'd say that you need to find out what impedence your next stage is
expecting to see.

Cheers,
Walt