I think some of you are saying the same thing in a different way.
Hybrid/EKT systems do use digital signalling for setup, features, lights, and buttons, but the voice stays analog on a separate pair from your mouth through the switch to another phone or CO line. They use (typically) the blue pair for voice and the orange pair for signalling. This can roughly be compared to a 1A2 system, where the line buttons and lights are controlled by different wires than the voice.
Digital/DKT systems convert your voice from analog to digital inside the phone and transmit it as digital from the phone through the switch to another digital phone, or convert back to analog in the CO card. Analog phones (2500 sets) on these systems connect to an analog card that does the analog to digital conversion on the card before going into the switch. They only use one pair from a digital phone to the switch.
Hope this helps.
