This Guy

http://www.jens-seiler.de/etrex/datacable.html

has this picture, plus some other good info

Here are the options for a “Sniffer” under linux

GTKTerm turned out to be the easiest way to read the stream

Here is a stream when the GPS is locked

$GPRMC,132644,A,3305.5972,N,09725.6079,W,0.0,185.3,281211,5.2,E,A*03

$GPRMB,A,,,,,,,,,,,,A,A*0B

$GPGGA,132644,3305.5972,N,09725.6079,W,1,03,1.6,274.4,M,-24.6,M,,*77

$GPGSA,A,2,02,,,,,12,17,,,,,,1.9,1.6,1.0*3A

$GPGSV,3,1,12,02,36,216,37,04,74,197,37,08,00,165,00,09,34,297,00*7A

$GPGSV,3,2,12,10,17,153,00,12,08,313,37,17,51,037,40,20,14,054,00*71

$GPGSV,3,3,12,27,42,276,40,28,45,114,00,32,00,034,00,46,54,181,39*76

$GPGLL,3305.5972,N,09725.6079,W,132644,A,A*5E

$GPBOD,,T,,M,,*47

$PGRME,30.8,M,50.0,M,58.7,M*1A

$PGRMZ,900,f,2*13

$GPRTE,1,1,c,*37

Here is a 232 converter:

http://www.yed.com/A429toNMEA.htm