Under normal circumstances, word clock is generated by one piece of equipment in your studio. From there it is connected in a "daisy chain" (not a "star") to all the other units that require word clock input, using BNC "T" connectors. At the final connection, it should be "terminated" with a resistance equal to the characteristic impedance of the cable used to make the connections. This is typically 50 ohms, but is not unduly critical. Eventide products in most cases allow you to select whether they have an internal termination.
The Eclipse has switchable termination. There is a jumper (JP1101) near the word clock input to enable it.
Early Eclipses were shipped with the termination enabled. We later decided to default it OFF and suggested termination using a BNC-T connector and terminator. That way, nobody had to remove the cover of Eclipse to adjust the termination.
To see if it's terminated, one could simply remove the cover and check the jumper. Alternatively, use an ohmmeter to measure the resistance between the pin and shield on the BNC connector after removing the cable. If it's around 50 ohms, then the termination is enabled.
These have switchable terminations. There is a jumper(JP250 on the main board) near the word clock input to enable it. They are shipped with the termination disabled. The termination can be enabled by connecting the jumper. Newer units have word clock on the main board. Because our practice in the past was to have the termination enabled by default, it would be best to check rather than assume either setting.
Older units - Orville only
Before word clock was standard, it was part of an option board assembly. On these units, the jumper was labelled JP101. How to set the jumper is described above.
Termination Check
To see if its terminated, one could simply remove the cover and check the jumper. Alternatively, use an ohmmeter to measure the resistance between the pin and shield on the BNC connector after removing the cable. If it's around 50 ohms, then the termination is enabled.
The word clock input has no termination. There is no jumper. When termination is required it should be done externally using a BNC T-piece and suitable terminator as described in the Operating Manual for V5.2 or later.
We use 51 ohm resistors for termination. There does not appear to be any "standard" for this function, so some will undoubtedly be using 75 ohm cable, in which case technically the termination should also be 75 ohms. While it is possible to change the termination impedance by soldering a 25 ohm resistor across the jumper posts, we have never heard of anyone needing to do this in a normal installation.
At present, all units are shipped unterminated with no jumpers installed.
Updated 20 March 2006