Abstract: In an integrated services digital network (ISDN) a telephone subscriber is physically connected to a telephone exchange by a digital signal subscriber loop which provides in time division multiplex (TDM), two B channels and a D channel. The two B channels are used for voice and data at a bit rate of sixty-four kilobits per second each. The D channel is used for packet data and for telephone signalling and supervision at a bit rate of sixteen kilobits per second. An ISDN D channel handler, in an exchange termination (ET) collects D channel data from and distributes D channel data to various ISDN subscriber lines. A frame processor, in the D channel handler, receives D channel information as it occurs in each of the receive channels. It directs D channel data to a receive buffer storage location where it is accessible by a translator. The translator recognizes information in the data which relates to supervisory and signalling functions, and passes the information to a central controller in the ET.