Abstract: A nonblocking switching system for communications systems is characterized by two identical blocking networks, each for being connected in series between sources and destinations to be selectively interconnected. One network actively establishes paths between the sources and destinations while the other, although conditioned to be able to provide such paths, remains inactive in a standby mode for establishing the paths should the active network fail. If a blocking state occurs in the active network before its maximum realizable capacity is reached, a nonblocking condition of the system is established by eliminating all of the paths in the inactive network, and then reestablishing the paths in accordance with a relatively simple algorithm that loads the network without a blocking state being reached before the network is completely full.

Abstract: A telephone system usable for example in hotels or the like and in which each of a plurality of telephone sets is equipped with a special status indicator or signal light as well as the usual bell, the system being characterized in that the indicator is automatically excited without ringing the bell by voltages applied from the ring generator whose output signal is connected across the tip and ring leads of a telephone line when the latter is placed in a special status (message waiting) by a status signal in the control unit. The ring generator is constructed to produce special status indicator excitation voltages during the "bell silent" intervals of its output signal, and the indicator is periodically actuated by connecting that output signal across the tip and ring leads of telephone sets, which are in the special status, during at least a portion of such intervals.