A universal DS-0 channelized format is provided wherein selected states of CAS bits are used to indicate to the transport mechanism when DS-0 channels are not being used for voice and are available for use for data transport. In addition, the T1 frame format carries CAS bits only in the first DS-0 channel, so that robbed bits are disabled and not used to carry ABCD signaling bits, thereby avoiding any risk of data corruption. Still further, a special CAS signaling value not defined as a CAS state, is employed in a frame nibble instead of a frame counter to indicate that the state is in the first DS-0 slot.