Description of Lucent RFTG-m-XO GPS frequency standard ver. 20.03.2007 Introduction The Lucent frequency and timing modules (modul number RF(T)g-m) had been used in GPS basestations for synchronization; there are various models available (quartz / rubidium or GPS based), made from 1998 to 2000; no official manuals or descriptions are available but the parts are described in newsgroups and amateurs like "time-nuts" have collected a lot of information (which is available in emails only, with a low "signal-to-noise ratio"); i have analysed and expanded this information, based on own observations; I will describe the RFTG-m-XO in details: it is a so called "GPS disciplined frequency standard" or GPSDO; that means the local OCXO is "disciplined" by the GPS based 1PPS signal on using a microcontroller; the OCXO parameters (like temperature drift and aging) are determined and the control voltage of the OCXO is calculated and applied; a "holdover status" is possible, when sufficient GPS signals are not available; so the resulting accuracy of the 1PPS/15MHz signal is much higher than based on a single quartz oscillator; the GPS receiver is a well documented Motorola VP Oncore; the GPS receiver's serial data (position, time and status) are internally as TTL signals available and can be used with TAC32 or other programs; output: via the serial interface (J6) time and status are transmitted once per second; (the text following should be read from the JPEG file ;-) ) Character 1-4 are unimportant, 5-6 are status, 12-19 shows GPS second (in hex format since 6.Jan.1980), 20-23 version number, 24-25 checksum; (the descriptions of the LEDs, J4/J6/J5/J3/J7/J2 and P1 are in english ;-) ) Connector J6 holds 1PPS output with a standard deviation of about 30ns compared to UTC; can be used for clock comparison or NTP server synchronisation; J6 pin1/2 holds a RS485 signal for longer transmission lines; there is also a sine signal available with a SMA connector (15MHz); this signal is based on the GPS controlled 10MHz DCXO (?); the latter can be identified easyly (should be buffered, when used for own purposes) frequency accuracy is about +-E-10 (tracking); Operation is easy; after connecting 24V DC on P1 and a GPS antenna on J7, the ON-LED show green light after about 15 minutes, indicating enough satellites; the output signals are valid then; to get a good "holdover" performance a longer operation period is neccessary; Sources: time-nuts-mailing list http://www.febo.com/pipermail/time-nuts/ Motorola Oncore http://www.corallinks/tmbroker/images/oncore_eng_notes.pdf