In each terrestrial station (12), a collecting circuit (97) collects those state information signals as a collected signal which represent states of operation of communication devices (94, 95). A state information signal sending device (101) sends the collected signal in a state information time slot...http://www.google.de/patents/US4715033?utm_source=gb-gplus-sharePatent US4715033 - State information communication in a TDMA satellite communication network with high frame availability
