One of the more efficient satellite communication systems is a DAMA (demand assigned multiple access) system which employs a limited number of satellite circuits controlled by a control computer located at a master station. In a DAMA system, all the satellite circuits are placed in a common pool and are assigned by the master station computer to the respective stations on demand. Upon completion of a call, the satellite circuits which were assigned to the stations participating in the call are returned to the pool so that they are available to be assigned to any other station when another call is placed.
In a DAMA network, the control computer at the master station may communicate with all the remote stations through a dedicated satellite channel, i.e. a common signalling channel (CSC), which provides a full-time, uninterrupted control link between the master station and the remote stations. Typically, the CSC modems of the remote and master stations operate on preassigned frequencies and may transmit digital signals between one another. These digital signals convey all the information that is required to set up a call through the satellite and to effect status monitoring of remote site equipment. One example of such a DAMA system is described in the U.S. patent to Yamato et al U.S. Pat. No. 3,548,108 and reference may be had thereto for a more detailed explanation of the various components employed in and operation of a DAMA satellite communication system.
Unfortunately, unlike terrestrial telephone networks, which employ a toll exchange to which a local exchange connects itself for the purposes of generating billing information, satellite communication systems do not require toll exchanges in the network hierarchy, so that an alternative measure is needed for generating billing pulses.