I am designing a system with an unknown number of RS-485 nodes and the installers (we know their ways) can not be relied on to set switches or any such operation. If I could find a locking connector with two identical pins and a contact that opened when a plug is inserted (the phone jack is "coax" and does not lock, which is needed) I could do the following:

 0------
in     | 
 0--   |      _____________________
   |   |      |
   *-- | --*--| transciever and '51
   |   *------|
   |   |   |  |_____________________
   |   |   |
   |   |   
   |   |   / 110 ohms
   |   |   
   |   |   /
   |   |   |
 0-    |   |
 out   |   |
 0-----*-- |
         ^-|  contact that opens when
              plug is inserted

I have Googled and Googled to no avail looking for such a connector, does anyone out there know of such a connector.

Alternatively, has anyone succesfully and precisely terminated with an analog switch IC included, then, of course, a loop connecting two extra poles in the out connector could make the analog switch open.

I am even considering using repeaters which, of course would lead to all connections being point to point and terminated, however the one character delay would be rather unpleasant to deal with and thus I would end up with 422 which entail the undesirable extra two wires.

Thanx in advance

Erik

PS please do not suggest cutting a connector and glueing a microswitch on it, this is a professional product,