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When I started doing telecom related projects in Australia I needed to learn about the protocols and terms. It took ages to figure out that when the US referred

When I started doing telecom related projects in Australia I needed to learn about the protocols and terms. It took ages to figure out that when the US referred to the "central office" what they meant was what we would call an "exchange" (formally "telephone exchange"). Why would a building that is primarily serving to interconnect and switch telecommunication circuits, and providing desks and rooms for workers would seemingly be a secondary function, if at all going by those windowless rural sheds, be called an "office"?

massysett 5y ago
This is just my uninformed guess, but in the old days this function did indeed require rows of desks with people manually plugging in wires to connect calls.
mattlondon 5y ago
Thank you. I too was confused by this just now - in the UK we would also call these "telephone exchanges".
djweis 5y ago
Before automated switching it actually was an office and housed staff and the telephone operators. After a hundred years the name stuck.
myself248 5y ago
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.
jbledsoe2112 5y ago
The buildings are called Central Offices. The switches inside are the actual pieces of equipment handling the calls. Yes, "telephone exchange" is also used, but not so much in the United States.

massysett 5y ago

This is just my uninformed guess, but in the old days this function did indeed require rows of desks with people manually plugging in wires to connect calls.

mattlondon 5y ago

Thank you. I too was confused by this just now - in the UK we would also call these "telephone exchanges".

djweis 5y ago

Before automated switching it actually was an office and housed staff and the telephone operators. After a hundred years the name stuck.

myself248 5y ago

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.

jbledsoe2112 5y ago

The buildings are called Central Offices. The switches inside are the actual pieces of equipment handling the calls. Yes, "telephone exchange" is also used, but not so much in the United States.