Altitude Encoder
 

I'm about to buy an altitude encoder. I see there is gray code and RS-232 output. My transponder uses gray code, but I notice there are encoders that have both outputs. Why would I ever need RS-232 output? Are there efis units that use RS-232?

Thanks.

Most of the EFIS and late modern transponders (except for low end) have a serial (RS-232) output. By using this output you only need one wire, whereas gray code uses 10 wires. If you have one of these EFIS and a gray code transponder, you will need a serial to gray code adapter. They usually sell for around $80.

EFIS and Transponder Wiring Example
 

Adding to Mel's comment...I just wired my Dynon D10A to my Garmin GTX 327 transponder.

The Dynon can output RS232 directly to the GTX327, eliminating the need for an encoder.

or...you can add an encoder and wire gray code from the encoder to the transponder

or...(if the encoder provides RS232 output) you can wire RS232 from the encoder to the transponder

or (as in Mel's example) you can buy a converter to convert from RS232 to gray code to the transponder (for an older model transponder).

Decisions, decisions...
Mike

I have this setup as well.
No need for a separate encoder.

My Dynon D10A feeds altitude to my GTX-320A. The GTX-320A only has gray code input, so I had to use the converter.
Still much cheaper and lighter than a separate encoder.