| 摘要 |
1277188 Automatic exchange systems; antiside tone circuit INTERNATIONAL STANDARD ELECTRIC CORP 3 Dec 1970 [5 Dec 1969] 57456/70 Headings H4K and H4R A conference circuit for up to ten or more subscribers comprises a common amplifier to the input of which each subscriber's transmitter is connected and to the output of which an individual receive amplifier for each subscriber is connected. The common and individual amplifiers are each operational amplifiers of the integrated circuit type and they each have a variable feedback circuit, for example resistances formed by printed circuit techniques, for adjusting the degree of sidetone whereby singing in the current talker's subset is prevented. (For Figure see next page) 6 |
