Abstract: A system for interconnecting orthogonally disposed printed circuit boards in first and second stacks comprises first contact members on facing edges of the boards of the two stacks used to interconnect the boards. A mother board is disposed perpendicular to and between the two stacks of boards. Second contact members are disposed on the same facing edges of the boards as the first contact members. They define with the first contact members a series of first multiway plug-in connectors along the respective edge of each board in the first stack and a series of second multiway plug-in connectors along the respective edge of each board in the second stack. The mother board comprises a distribution network in the form of an array of conductive tracks assigned to distributing signals to the boards. The mother board also carries connecting contact members and distribution contact members connected to the distribution network.

Abstract: A signal peak detector which can be used for echo suppressors, has a memory in which is written a value which is variable as a function of the incident signal and represents the peak sought, an attenuator of the memorized value; four comparators; three of which compare the instantaneous value of the incident signal with, respectively the memorized value, the attenuated memorized value and a fixed threshold, and the fourth of which compares the attenuated memorized value with the fixed threshold; and a control unit which modifies the memorized value as a function of the result of those comparisons.

Abstract: The invention comes within the field of four-wire telephony. To avoid the closing of a loop between the two unidirectional channels, a half-echo suppressor is provided for each terminal, which comprises mainly a speech detector for the emitting channel, said speech detector having two operational modes: the first sends out a speech indicator signal based on the characteristics of amplitude and sign change on the emitting channel whereas the second compares the amplitude on the emitting channel and the amplitude on the receiving channel and is effective when the receiving channel is active. The invention applies more particularly to a PCM network in combination with a concentrator which uses the inactivity periods of the circuits.

Abstract: The invention comes within the branch of digital data transmission on a telephone line having four wires comprising echo suppressors. In order to be able to neutralize these suppressors during a simultaneous bilateral data transmission, a neutralization signal is developed in a purely digital device basically using a PCM coder, counting the changes in sign of the line signal. The use of digital filters to identify the characteristic frequency preceding the transmission is thus avoided.