Hello everyone, If anyone is interested, I have created a HOWTO on running a Motorola GPS receiver connected to a CentOS 7 box via serial port (com1), with 1PPS over DCD. The trick here is that CentOS 7 uses systemd and setup was a bit different. Anyway, everything works. The result is a highly accurate NTP server, Stratum 1. Here is the documentation. http://www.maximaphysics.com/Centos_7_GPS_Setup.html Let me know if something does not look right. -George, N2FGX