Abstract: A communication system includes a communication switching office having a transceiver for receiving/transmitting a message from/to a data terminal using a communication system, and a management system including a central controller receiving/transmitting the message from/to the communication switching office. The central controller is responsive to the message received from the data terminal, and receives data in the message received from the data terminal. The data terminal transmits to the management system on a message channel. The message channel includes multiple messages from multiple data terminals. The management system receives the multiple messages per message channel or TDM group, and allocates message channel bandwidth for each of the multiple messages to the data terminal responsive to the data terminal call request received on the signalling channel.