| Word | Description |
| D-channel | Signaling channel in ISDN circuits. A 24 channel, PRI circuit will have 23 B-channels and 1 D-channel. E1 circuits (used outside of the US and Canada) have 31 b-channels and 1 D-channel. |
| Dialer | A computer that is used to make phone calls. SpitFire Dialers come in 2 main varieties, Auotdialer and Predictive Dialer. |
| Dialogic Card | This card is the standard Telephony card used in all SpitFire Dialers that are interfacing with either analog or T1 lines. SpitFire Dialers use Dialogic cards from 4 lines per card, up to 48 lines (2 T1's) per card. SpitFire Dialers can also be built using Dialogic E1 cards for Dialers in locations outside of North America. |