Channel-associated signaling

Channel-associated signaling (CAS), also known as per-trunk signaling (PTS), is a form of digital communication signaling. As with most telecommunication signaling methods, it uses routing information to direct the payload of voice or data to its destination. With CAS signaling, this routing information is encoded and transmitted in the same channel as the payload itself. This information can be transmitted in the same band (in-band signaling) or a separate band (out-of-band signaling) to the payload.