Two-party telephone system

Abstract

Abstract The present invention relates to a two-party telephone system intended for external calls to and from each of the telephone sets included in the system, and speech connection between said telephone sets and conference calls between the telephones and an external subscriber. All these facilities are achieved through a two-wire connection between the telephones and require transmission of at least three different information conditions between the extensions included in the system. Each of the telephone sets comprises a visual indicating means Iα for busy marking and a voltage source E which by connecting its voltage through the two-wire line activates the device Iβ in the other telephone. An acoustical indicating means BZ which is activated by polarity reverse in said voltage source in the other telephone is also included in order to indicate that the telephone in which the polarity reverse has occurred wishes speech connection. To each telephone in the system is also connected an eavesdrop indicating means Iβ which is activated in both the telephones when the voltage through the control device is increased by series connection of said voltage sources in order to indicate unintentional monitoring and that, at external call, both the telephones are connected respectively.

Inventors

• 👤 Sten Evert Magnusson

Bibliographic Details