Telefonaktiebolaget Lm Ericsson (publ)

Anders Olof Lindstrom

Hans Magnus Broberg

Anna Kristina Bostrom

In the connection of a number of telephone sets to a private branch exchange, control information is communicated between the telephone sets and the exchange set in such a way that a bidirected conversion unit is required. In order to provide a high degree of service at a reasonable cost the telephone sets are collected in groups which share a generally smaller number of conversion units. By way of suitable control devices and switch units in the forwarding of control information, a suitable non-occupied conversion unit can be selected.

Apparatus for communication between a telephone exchange and connected

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.

Testing of subscriber lines in a digital switch

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.

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Vallingby, Sweden

Anders Olof Lindstrom