| 摘要 |
PURPOSE:To prevent bothway collision by a simple method only by providing a common start supervisory relay to several bothway calling trunks by making use of the start supervisory relay as a pattern-relay control gate relay. CONSTITUTION:In trunk common circuit COM of an exchange brought under pattern, control, start supervisory relay SP is provided and through the make contact of this relay SP, several bothway callinh trunks BWT are connected. When an office exchange is placed in a calling state at the time of incoming, relay R operates and relay SP is OFF being connected via make contact P<0> of gate relay P. To connect calling subscriber SUB to calling trunk BWT next, a central controller selects calling trunk BWT and before network NW is bus-closed, corresponding relay P is operated to read the state of relay SP via scanner SCN, so that when incoming arrives from the office exchange, relay SP is put into operation. |
