Abstract: In a communication network, a source frame relay unit responds to a signaling message from a source terminal by determining whether a communication link has a bandwidth sufficient to transmit a sound signal at a predetermined speed in a frame relay format, and forwards the message toward a destination frame relay unit to establish a connection if the link has a bandwidth sufficient to transmit the sound signal, or returns a busy tone otherwise. Responsive to a preamble tone signal from a destination terminal, the destination frame relay unit determines whether the link has a remaining bandwidth that can support the difference between the predetermined speed of the sound signal and a speed requested by the preamble tone signal to transmit facsimile signals in the frame-relay format. If so, the source and destination terminals are allowed to exchange facsimile signals at the requested speed. Otherwise, the terminals are controlled to exchange facsimile signals at a speed lower than the requested speed.

Abstract: In an inter-PBX routing apparatus, calls from channels of different service categories to a destination are normally carried by a first route. A controller determines the available bandwidth remaining in the first route, classifies the channels as a first or a second category if they cannot or can tolerate delays when establishing an alternate route, respectively, or a third category if they do not require the second route when the first route is overflowed. A second route is established on a pre-assigned basis when the bandwidth of at least one idle channel of the first category is greater than the available bandwidth and on a demand-assigned basis in response to a request from a channel of the second category having a bandwidth greater than the available bandwidth.