Unfortunately, whereas "RS-232 and NMEA" are very much a standard,

Hi, Joel,

Actually, RS-232 has always baffled me, and from some measurements I made it
doesn't seem to be a very strict standard. For example, the waveform coming
out of the GPS receiver was +/- 5 V, whereas I have seen the waveform out of
the RS-232 on the computer at +/- 12 V. Is the voltage level arbitrary?

Al