"DS1 / ISDN Trunk Circuit Pack. Supports 24 trunks using Robbed Bit Signaling or 23 trunks using Common Channel Signaling. Provides interface to DS1 Tie Trunk plus ISDN PRI message-Oriented Signaling to interface with a host computer, another Definity or a public/private network. Note: requires Integrated CSU (63185) or DS1 cable with external CSU."
