SE302791B - - Google Patents

Abstract

1,183,941. Automatic exchange systems. TELEFONAKTIEBOLAGET L. M. ERICSSON. 2 June, 1967 [2 June. 1966]. No. 25690/67. Heading H4K. A lock-out arrangement for connecting one of a group of apparatus units to an idle one of a second group of units comprises two sets of bi-stable devices which provide " tree " connections between wires individual to the units of each group and a common point. The bistable devices may be 2-winding polarized relays or equivalent electronic circuits. In Fig. 1, one of a number of registers REGL storing a wanted number is connected to an idle one of 4 markers M41 over a cross-bar switch RSM under the control of common equipment RMM comprising two sets of bistable relays. Relay RR1 in the calling register REGL closes a circuit to relay MR3 in the first idle marker, assumed to be MH1, through the relevant relay windings, and these complete a circuit for MR2 in series with select magnet SM1, whereupon operating BM establishes the cross-bar connection. MR1 energizes in series with RR2 and the common equipment is released. A pulse on wire a causes the transfer over the stored number over common wires t 1 . . . t m to a marker store MR. A faulty marker is put out of service by alarm relay AL, and a thermal contact r 1 becomes operative if RR2 fails to pull up. A similar arrangement employing electronic circuits is described with reference to Fig. 2 (not shown). A similar lock-out arrangement, Fig. 3 (not shown), serves to connect a marker to an idle junction in a selected traffic route, the identity of the junction being signalled from its line circuit to the marker for the purpose of establishing the connection. There is provision for preventing the repeated selection of the same faulty junction.