c0.prv.gps.s1 uses a Garmin GPS 18 OEM LVC module connected following Philip M. White's GPS refclock instructions. gpsd monitors the serial port and provides both NMEA and PPS outputs to ntpd using the shared memory refclock driver.
server 127.127.28.0 minpoll 4 maxpoll 4 fudge 127.127.28.0 time1 -0.352029 refid GPS server 127.127.28.1 minpoll 4 maxpoll 4 prefer fudge 127.127.28.1 refid PPS server c0.prv.dcf.s1.ntp.faelix.net peer server c0.prv.dvb.s1.ntp.faelix.net peer server l0.prv.dcf.s1.ntp.faelix.net peer server c0.prv.ext.s2.ntp.faelix.net server m1.prv.ext.s2.ntp.faelix.net server time.twc.weather.com iburst server 127.127.1.0 fudge 127.127.1.0 stratum 11