| 摘要 |
PURPOSE:To extremely simplify the constitution and the control of a privacy telephone circuit, by performing the branch connection of two telephone sets to a trunk line. CONSTITUTION:The incoming calls given from trunk lines L1 and L2 are fed to terminals 6 and 1 of a privacy telephone unit 16 and then delivered to terminals 2 and 3 to actuate a relay LA. Then a transistor TRQ21 is turned on at a contact la<0> to actuate a relay PA. Under such conditions, if a slave telephone 3 is interrupted, a relay LB works. The line L1 is separated from the line L2 via contacts Pa<0> and Pa<1>, and as a result the telephone 3 is set under a privacy call state. In case the telephone 3 becomes busy earlier, the relays LB, PB and RV work with a relay T recovered. In this case, a main telephone 2 is interrupted, and as a result the relay LA is actuated by contacts pb<0> and pb<1> of the relay PB. The channel of the telephone 2 is not connected to the lines L1 and L2 to secure a privacy call state. |
