CLLI (pronounced "silly") is a Bell System acronym standing for Common Language Location Identifier. It was a standardized way of describing locations and significant pieces of hardware at those locations.
The short eight-character CLLI is broken down as follows:
Clear as mud, right? Well, here is a working example from my neck of the woods: MPLSMNDT. The first four letters, MPLS, indicate Minneapolis. The next two, MN, are for Minnesota. And the last two, DT, are for "downtown."
Okay, now that you have a clear idea of that concept, you will know why I used the imaginary CLLI Code of EDPRMNEV for my switch located in the Edenvale neighborhood of Eden Prairie, Minnesota.
But wait! There's more! There are three add-on characters at the end of a CLLI Code that indicate the piece of equipment at that location. The letter "K" in "K01" would indicate a DACS, or digital cross-connect system. "DS" or "DC" in "DS0" or "DC0" would indicate a digital end office. "29T" would indicate a toll tandem, with the "T" being the indicator of a toll tandem.
As mentioned above, CLLI codes in the Collector's Network are largely imaginary, but it is encouraged that the naming conventions shown above be followed for that "faux" authenticity.