The incoming CO ring first activates the R relay in the line card. The R relay starts the interrupter motor by grounding the MS ("Motor Start") lead. The interrupter has cams and contacts that produce the "0ne second ON, three seconds OFF" cadence, that is fed to the CA lead on the line cards via the RN ("Ring iNterrupted") lead. There is an option block on each line card that allows the installer to provide (1) interrupted ring, (2) steady ring or (3) ground to the CA lead.
If the central office double ring you refer to is what the RBOC's call "distinctive ring" and you wish to pass this along via the interrupter circuit / CA leads, you are not going to be able to do that. The interrupter will give you 1 ON, 3 OFF regardless of what cadence, or cadence fragment, it detected to get it going in the first place.
If your installation is small enough (Is this your own set-up, being used as a "hobby" sort of thing?) then you can wire the ringer in each set, or provide EB-type line ringers, so that they follow the incoming CO ring directly. (You will need one ringer per CO line.)
If you are clever with electronics, you can produce a circuit board that will take steady generator and make psuedo-distinctive ring cadences, and send them out via the CA leads. You would use the output of this circuit instead of the RN output of the interrupter.
Last edited by Arthur P. Bloom; 11/21/12 08:13 PM.
