Abstract: A device for testing line connections at a telephone exchange includes a combined generator and comparator for generating a bit sequence of pseudo-random type and for comparing a received bit sequence to a generated bit sequence. A generated bit sequence is through a line connection forwarded to a telephone set and back again to the generator and comparator, where the received sequence is compared to the forwarded one. The number of bit errors occurring in the transmission is a measure of the transmission quality of the connection. A selector device selects one of several line connections which is to be tested. Only one testing device is required for testing a number of line connections which through the same pair of one serial output line and one serial input line are connected to a telephone exchange.

Abstract: A method for determining the length of a telephone line from an exchange to a subscriber. The method is based on the availability in the exchange of so-called line circuits, each having a given amplification factor G for the signal transmitted from a given subscriber through the line, this factor being stored and made available to the microprocessor of the line circuit card. The attenuation for each unit of line length D between the exchange and the subscriber is known. Since these magnitudes are known, the line length L is calculated in the microprocessor from the equation L=k.G/D, where k is a constant which is calculated for a given determined length, amplification factor and attenuation/length unit.