| 摘要 |
<p>1,216,627. Automatic exchange systems. NORTHERN ELECTRIC CO. Ltd. 30 May, 1969 [6 June, 1968], No. 27565/69. Heading H4K. In a system in which, for an outgoing call, a calling subscriber is connected via a line frame, an originating junctor and a trunk frame to an outgoing trunk circuit and in which a sender is connected to the originating junctor during outpulsing, supervision of the connection is vested in the junctor during sending and then in the trunk circuit when sending ceases and the sender has been disconnected. Crossbar switches are used in the line and trunk frames. The system is distinguished from the No. 5 crossbar wherein the sender is connected to the outgoing trunk, and originating junctors are not utilized (Fig. 1, not shown). Details.-It is assumed that the connection is completed up to an outgoing trunk 34 in which a relay ON is operative to an earth on the sleeve lead S. When sufficient digits have been accumulated in a register sender 35, a relay D is brought up in the originating junctor 32 whereby a holding earth for the hold magnets H in the trunk frame and for the relay ON in the trunk is applied to the sleeve. The digits outpulsed from the sender are passed over the Tip and Ring leads to a special signalling path associated with the trunk. When sending ceases, relay D is dropped thus removing earth from the sleeve and allowing low resistance relay EP in the trunk circuit to come-up in series with ON (which is slow to release). A resistive holding earth is thus reapplied to the sleeve via EP until such time as full ground is applied from the calling or called party's supervisory circuit. EP also switches through the talking path at its contacts EP1, EP2.</p> |
