Narrowband integrated voice/data networks require that congestion control and bandwidth management techniques be implemented in order to provide the desired quality of service. An adaptive voice/data switch has been developed to demonstrate the application of the Sinusoidal Transform Coder (STC), a low bit-rate digital speech coder, to the implementation of integrated networks. In this work, an integrated network management and control protocol is designed and implemented. The protocol exploits the unique capabilities of the STC for congestion control in a narrowband integrated network environment. A software testbed is constructed to evaluate the speech coding technique and to verify the protocol functionality. The results of informal listening tests on several simulated conversations suggest that this coder is well-suited for bandwidth reallocation based on dynamic rate adjustment. The performance of the adaptive voice/data switch congestion control mechanism is studied using simulation.