Lorenz GPS and NMEA

I managed to get a Lorenz chart plotter and Raymarine DSC Radio for decent prices on the world famous flea market, however there were no instructions available for the plotter, and for once there was scant little information about it on t'web.

After finding the menu settings on the Lorenz and discovering that it was sending out NMEA V1.X sentences, I then looked up the communication protocol and found out it is based on RS232, i.e. ground and +5 V signalling.

So all I had to was strip back the wires, plug in the scope and test each one to find the +5V signals. Second attempt gave me this:

Now I had found the signal wire, I just had to hook it all up:

And sure enough the radio detects the GPS information :)