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Trimble Resolution T Timing GPS module 12ns 1pps
The Resolution T receiver outputs a 1 Pulse-per-second (1 PPS) timing signal accurate to within 15 nanoseconds of GPS or UTC (1 sigma) when using an overdetermined solution in a stationary mode.
NMEA Messages:    

GGA, VTG, GLL, ZDA, GSA, GSV and RMC
The kit includes an active, external     5-VDC Bullet-style antenna, 50 feet of RG-59 cable, and an AC/DC power adapter. The starter kit enclosure includes a mother board that provides serial output, and a serial interface cable. A reference manual and monitor programs are provided on CD-ROM.
Fully Featured, Low Cost, Embedded GPS Timing Receiver
I've come across this timing GPS module on eBay I am waiting to test this to see if I can use the 1pps .This will be used alongside tardis software which monitors the computer time clock.