Terminal interface device

摘要

A unit which allows a data transmission device such as a modem or FAX to be connected to a telephone line that is employed as the communication channel for a supervised alarm system. The poll and poll response signals and low-tone associated with a supervised alarm system would interfere with the data signals flowing to and from a modem/FAX if allowed to be present on the telephone line simultaneously. The present invention will disconnect a modem/FAX from the telephone line during data transmission if an alarm condition arises, by monitoring the low tone status of the alarm system. A low tone filter is provided to improve data transmission and connection speeds. Low tone attenuation is synthesised by the present invention to indicate off-hook status to alarm monitoring equipment at the telephone exchange. <IMAGE>