Abstract: A circuit arrangement for telecommunication installations, in particular, telephone exchange installations is disclosed in which type information is sent ahead of each communication to be transmitted. In bidirectional communication transmission with different possible communication types, type information announcing the respective communication type is sent ahead. In the receiving equipment the beginning of the arrival of type information is recognized and immediately, that is, almost simultaneously, an assortment of type-specific message corresponding to each of the possible communication types is transmitted in the opposite direction, of which each indicates the readiness or non-readiness for receiving a communication of the respective type.

Abstract: A concentrator equipped with two processors is connected via two corresponding channel systems to a higher ranking exchange. Both processors operate independently of each other and poll all subscriber line circuits for switching codes. In the event that a channel system malfunctions, but the concentrator processor is operational, one processor transmits request signals, as well as an emergency operating state signal, to the subscriber line circuits. If the processor itself malfunctions, it transmits request signals and, in addition, an out-of-order state signal. The emergency operating signal and out-of-order signal are stored by each of the subscriber line circuits. Switching codes are transmitted to each of the two processors when both of these processors are in standard operating mode or in emergency mode.