DID - The presentation of the last 2, 3 or 4 digits of a dialed telephone number to a PBX to switch the call to the relevant employee. Commonly used for CTI, Audiotex and IVR systems to activate different services depending on the number dialed, even though the call is delivered over the same physical telephone line. Known in Europe as Direct Dialling Inward or DDI (Note the spelling difference for the word "dialling" as well).