Hello Ronald,

The Tronisoft adapter is really a classical adapter, using the famous MAX232 RS232-TTL levels converter. On the RS232 side, you get signals so:

1 = -7V to -12V
0 = +7V to +12V

On the TTL side, you get signals so:

1 = +5V
0 = 0V

(note that signals are inverted between sides).

The 4207Papy is the same version as their standard one, but including:

- the little jumper to bring power on PON9 off the sub-D, so it power-up the BT adapter
- spcial connectors for both power supply and TTL signals, so Claude's cable is easy to plug, without any risk inverting polarity

I also omitted to say that the Tronisoft module includes the 5V voltage regulator (Merlin output is from batteries, so from 9V to 12V).

You can use any design based on the MAX232 chip (there are plenty on the net, but non including the voltage regulator *and* a nice form factor).

Another solution is to use a BT-serial adapter which outputs TTL signals...