Specifications

APPENDIX A. INSTALLATION 29
• switch 10 - ON (10MHz clock on pin 4)
• switch 4 - ON (1Hz pulse on pin 8)
• all other - OFF
Also some clock cards have to be installed into the computers. In the computer with the
GPS card you have to put a master clock card and in the others - slave clock cards (in fact
you c an put master cards in all computers). The GPS is working fine if the green LED
is ON (on the connector of the board). You can also see if the GPS is working using an
oscilloscope. You should b e able to see the 10MHz and the 1Hz signals.
NOTE: The signals are available only after the GPS has synchronized with the satellites
- mbgstatus should show something like in Figure A.1.
A.3 Cable connections
If a local group consists of only one computer then the cable connections are the following:
GPS serial port – pin 4 (10MHz -clock) → input #1 on the clock board
GPS serial port – pin 8 (1Hz PPS) → input #3 on the clock board
output #2 (fire out) on the master clock board
→ input #4 on the same board (fire in)
If the local group contains one or more slave clock boards:
GPS serial port - pin 4 (10MHz clock) → should be distributed to all clock cards
using T connectors - at input #1
GPS serial port - pin 8 (1Hz PPS) → should be distributed to all clo ck cards using
T connectors - at input #3
output #2 (fire out) on the master clock board → should be distributed to
all clock cards using T connectors - at input #4 (fire in). From the last clock card in
the chain it should return to the master clock cards also at input #4.
NOTE: Be careful about connecting the slaves & master clo ck cards! The inputs of the
master should be the last to be connected, as the masters has the terminators. So even if
”fire out” has to be plugged back in the master’s ”fire in”, it should be first teed through
everybody else’s ”fire in” and be plainly connecte d to the master ”fire in” to get the input
in the master and to get a terminator. More information about this: the logbooks and
Brian himself.
A.4 Software
The software is made up of 2 kernel modules and some driver programs that control the
synchronization procedures.