METHOD OF DETECTING HAZARDOUS LINE VOLTAGES OVER A TWO-WIRE LINE

摘要

A method of detecting hazardous line voltages over a two-wire line for transferring digital information. At one end the line is terminated by a fork and an apparatus for adaptive echo elimination. This apparatus generates a digital signal constituting an unambiguous measure of the difference between the line impedance and the fork impedance. This signal is compared with two digital limiting values and alarm being given should either these two values be exceeded.