OK - I played around for a bit and got the advanced code setup working on the 2116. The process for testing a code is the same as the 1995:

- Press the device key
- Press the 'P' key (don't hold it)
- Enter the 3 digit code
- Check for a response from your equipment

The process for programming a code is a bit different:

- Press the device key
- Press and hold the 'P' key until the display reads 'CODE SET'
- Scroll down to 'KEYMOVER'
- Press SELECT
- Screen reads 'FROM MODE'
- Press the device key
- Screen reads 'FROM KEY'
- Press the 'P' key (don't hold it)
- Display reads 'SYNT'
- Enter the 3 digit code and press SELECT
- Display reads 'TO MODE'
- Press the device key
- Display reads 'TO KEY'
- Press the target key
- Display reads 'SUCCESS'