Abstract: A communication system transmits packetized voice data from a voice source to a voice destination. At the voice destination, the packets are accumulated in a buffer, sequentially played out and the time the packet waits in the buffer is monitored. The time future voice packets are played out is accordingly adjusted.

Abstract: An apparatus for and method of checking the validity of one or more directory numbers in a device for interfacing communications equipment to a digital telephone line, wherein the device is capable of accessing at least two channels on the digital telephone line, each channel having a directory number associated therewith, including: instructing the device to establish a plurality of protocol layers; initiating a call from the device over a first channel of the digital telephone line to the device over a second channel of the digital telephone line only if the plurality of protocol layers are established; and determining if the call is received by the device over the second channel to check the validity of the directory number associated with the second channel.

Abstract: An adaptive digital data unit (600) initiates and successfully completes a remote loop back test. The adaptive digital data unit (600) has a controller (610), a local transmitter (620), a local receiver (640) a timer (622) and a detector (634). When a remote adaptive digital data unit (600) transmits a first data sequence and a second data sequence, the local adaptive digital data unit (600) receives the second data sequence from the remote digital data unit and determines if the second data sequence matches one of two predetermined data sequences. If so, a test successful flag is generated.