| 摘要 |
606,805. Loud-speaking telephone systems. AUTOPHON AKT.-GES. March 8, 1945, No. 5804. Convention date, Nov. 6, 1942. [Class 40 (iv)] In a loud-speaking telephone system, a substation is provided with switching means by which transmission in one or both directions may be blocked although a voice frequency calling signal is always permitted to pass, so that a calling subscriber may be prevented from over-hearing sounds in the room of the called subscriber. The transducer EW is connected by switches u1, u2 (controlled by means unspecified) to the amplifier V either for use as a transmitter or as a receiver. Opening of switch SH1 disconnects outgoing speech currents. Opening of switch SH2 unbalances the differential relay X at the exchange, thereby preventing speech signals in either direction. Calling tone is applied by relay R (operated by means unspecified) which also parallels the two coils of relay X which is thereby balanced and so released, so that the tone is not only sent to the called subscriber but also to the calling subscriber for monitoring purposes. Switches SH1, SH2 may be independent or operated by the same lever, but in the latter case a removable metal link is provided across SH2. |
