Telefonaktiebolaget Lm Ericsson (publ)

Juho Arras

Walter Herbert Widl

Mats C Olstedt

Mats Orjan Mattsson

An arrangement for feeding the subscriber's lines (10) of a public exchange with reduced line current upon the occurrence of a power failure, when the temperature within the public exchange or the temperature of individual components, mounted on circuit boards on which line interface circuits are present, exceeds a predetermined reference value, when the length of a subscriber's line is less than a line length reference value, or when the conversation time on a subscriber's line exceeds a conversation time reference value. All subscriber's lines or individual subscriber's lines only are fed with the reduced line current for a restricted time (FIG. 5B).

Power down feed

A voltage shock protection circuit having two anti series connected field effect transistors adapted for being connected between a conductor and a protected circuit for connecting the protected circuit to the conductor and also protecting the protected circuit against voltage transients possibly occurring in the conductor, the voltage transients having excessively high or low potentials that could damage the protected circuit. The voltage shock protection circuit has a voltage sensing circuit connected to the protected circuit and to the conductor so that it is sensitive to voltage drops across each of the anti series connected field effect transistors and adapted such that when either of the voltage drops becomes sufficiently great one of the field effect transistors is pinched off. The voltage sensing circuit may include a field effect transistor. The two anti series connected field effect transistors and/or the field effect transistor in the voltage sensing circuit are dimensioned such that in their conductive state they become saturated on the occurrence of a voltage transient with a damaging potential.

Voltage shock protection circuit

A method and an apparatus for measuring the bit error frequency in a cable caused by crosstalk from at least one disturbing pair to a disturbed pair at transmission of a 3-level coded PCM signal utilizes the fact that a PCM signal transferred on a pair and the disturbances superimposed on this signal by crosstalk from other pairs are mathematically uncorrelated. The amplitudes of the disturbances measured on the disturbed pair are sampled after equalization in a regenerator with a sampling frequency which equals the bit time frequency of the PCM signal intended for transmission on the pair. The number of detected sampling values whose magnitude exceeds a certain threshold value is a function of the estimated bit error frequency.

Growing community of inventors

Stockholm, Sweden

Juho Arras