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555 switchboard tie trunk questions

Started by trainman, January 18, 2017, 11:23:32 AM

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trainman

For home use, can i connect two pbxs together using the regular central office trunk modules? Or do i need to find the appropriate tie trunk unit and relay strip?




Victor Laszlo

#1
A tie trunk is a specialized bunch of equipment, with a circuit at each end (at each PBX).  The circuit would appear on a trunk jack at each (manual) PBX or would be assigned a special dialing code if used between PABX's.

Please note that the Bell System used the term PBX to describe both manual and automatic exchanges. The "other" part of the industry differentiated between manual and automatic by using PBX and PABX for the two types.

Without the extra equipment, which be hard to find, you can assign a station circuit on one board to a truck circuit on the other board. A call from board #1 would be set up by inserting a station cord in the station jack and ringing into the truck ckt at board #2.  A call from board #2 would be set up by inserting a trunk cord of board #2 into the trunk jack, and the call would come in as a station off-hook signal at board #1. That request for service would be handled as a station-to-trunk or a station-to-station call on board #1.

An alternative, which would be less operationally cumbersome, and be symmetrical, would be to use a two-way auto ringdown circuit such as the SanBar 4415, or the Viking DLE-200B.  One of the two ports would appear on a truck ckt on each board. There's a Viking on Ebay right now for $40 free shipping, which is a good deal.



trainman

Yes. I might add one bord is a 555, and the other is a cordless 505, so, trunk ringing on from the 505 might be hard, unless its with a magneto.

trainman

I was thinking trunk to station from board 1, and station to trunk on board 2

trainman

I purchased the Viking  DLE-200. The Viking Ring Down unit works for calling between two switchboard trunks.