The FireFly-1C GPSDO provides three GPS disciplined 10MHz and 100MHz outputs in a form-factor that is designed to address laboratory and 19 inch rack-mount equipment reference requirements. Based on a very fast warmup and very stable TCXO, the unit provides two very low phase noise isolated 10MHz sine wave outputs, and one low phase noise 100MHz sine wave output, all on SMA connectors. It also provides instant-lock capability to an externally supplied optional 10MHz reference (with +/-40Hz lock range). Switch-over to the external reference is automatic, and indicated by on-board LED’s as well as optional external “REF DETECT” and “GPS LOCKED” LED’s. The FireFly-1C board supports both USB and TTL-level serial ports (RS-232 level is optional), and has built-in SCPI and NMEA command and control sentences for easy integration. The FireFly-1C board runs either from USB power, or from an external +5V supply, and both USB power and the external +5V power can be applied simultaneously for redundancy, and overall typical power consumption is 1.1W.