Re:Telephone Central Office Building Pictures
by myself248 on Saturday October 09, 2021 @12:55PM
(#28811403)
In the US, the terminology goes like this:
The "office" is the building, the "wire center" is the collection of circuits that terminate in a given location, the "frame" is physical hardware that holds those circuits and a group of staff who service them, the "exchange" is a legal and software concept for lines with a particular billing (local vs toll-call) relationship to each other, and the "switch" is hardware that implements the exchange among other things.
These all refer to subtly different things. One office can have several exchanges in it. One exchange can be served by multiple switches, or one switch can serve several exchanges. Office consolidation can mean multiple wire centers in one office. And larger offices often have multiple frames which have multiple frame techs working them because they're a long walk from each other.
Also within the office is transport equipment, historically called "toll" equipment since calls leaving the office were expensive, but that's very much a legacy term at this point. Transport equipment is transparent both to call routing and data traffic, so you don't see it on a billing statement or traceroute or whatever, but in any given office, the transport (and associated cross-conneect) equipment probably outweighs the switch by an order of magnitude.
Within a CLLI code, the first eight characters are the office, then the next three are the exchange. For instance, DTRTMIVTDS0, is the DTRT MI area, VT office, DS0 switch. Historically there was another switch in the building called DTRTMICG0, but it's been decommissioned and the lines moved to DS0. Transport equipment has CLLI codes too but outsiders seldom see them.
The "office" is the building, the "wire center" is the collection of circuits that terminate in a given location, the "frame" is physical hardware that holds those circuits and a group of staff who service them, the "exchange" is a legal and software concept for lines with a particular billing (local vs toll-call) relationship to each other, and the "switch" is hardware that implements the exchange among other things.
These all refer to subtly different things. One office can have several exchanges in it. One exchange can be served by multiple switches, or one switch can serve several exchanges. Office consolidation can mean multiple wire centers in one office. And larger offices often have multiple frames which have multiple frame techs working them because they're a long walk from each other.
Also within the office is transport equipment, historically called "toll" equipment since calls leaving the office were expensive, but that's very much a legacy term at this point. Transport equipment is transparent both to call routing and data traffic, so you don't see it on a billing statement or traceroute or whatever, but in any given office, the transport (and associated cross-conneect) equipment probably outweighs the switch by an order of magnitude.
Within a CLLI code, the first eight characters are the office, then the next three are the exchange. For instance, DTRTMIVTDS0, is the DTRT MI area, VT office, DS0 switch. Historically there was another switch in the building called DTRTMICG0, but it's been decommissioned and the lines moved to DS0. Transport equipment has CLLI codes too but outsiders seldom see them.