A terribly uninformative guide to cross connect boxes, RTUs, SLCs

For some reason beyond me, in all of the years I've messed around with phones, be it working with them or doing things as a hobby, I can never remember the name for this:


So I wanted to create this post so in the future when I go brain dead I don't have to go search around for it for 10 minutes. It breaks down like this:

  • Cross Box or Cross-Connect Box – Most common name, but in Ma Bell terms it usually refers to ones slightly smaller which contain jumpers from customer to the central office. These aren't to be confused with VRAD which are similar, but smaller, and often sometimes next to cross boxes or remote terminals.
  • Remote Terminal – Also sometimes called this, and so-called because they were like a tiny remote central office. These, unlike regular cross boxes, have slots for cards of what kind of circuit was being installed. For example a SDN line would have a card that takes two slots. Another sign of a Remote Terminal Unit versus a regular Cross Box is that RTUs have batteries in them. Some RTUs are bigger and are buried underground with sump-pumps and air conditioners and fancy stuff.

    Everyone loves slots
    Slots inside a Remote Terminal, a more modern one, smaller, at an industrial site.
  • SLC or SLC96 – Sometimes referred to as this, but these contained pair gain multiplex equipment in them. SLC itself stands for "subscriber loop carrier" or "subscriber line carrier". The 96 though refers to the fact it broke down into 96 lines.

And there we go, things I can never remember.

Thanks a lot to the phone woman for some extra insights into this post.