Common carrier switching center in which trunks and loops are terminated and switched.The C.O. provides service to the general public, possessing the necessary equipment and operations management for terminating and interconnecting subscriber lines and trunks or trunks only

Circuit
Total path between two terminals over which one way or two way communications may be provided.

Conference all
A service feature that allows a call to be established among three or more stations in such a manner that each of the stations is able to communicate with all the other stations.

Contract

Legally-binding agreement between a customer and a vendor to provide, services or products for a specific price, a specific quantity, quality, over a commonly agreed period of time.

Cutover

Specific time and date that a phone number, service, etc. is scheduled to be moved from one carrier to another. e.g. moving a phone number from ATT to Qwest.

CSU

Circuit Switching Unit

DAL - Dedicated Access Line

Non-switched circuit from carrier to customer.

Deactivation

The request to terminate a service.

Also the process of terminating a service.

Dedicated Line

A leased Private Line obtained through a telecommunications carrier.

Dial Tone:
A tone setup in a phone system to indicate to the calling party that the equipment is ready to receive dial or tone pulses.

DID

Direct Inward Dialing