Abstract: An adapter terminal unit is designed to connect to the time-division switching center of which it forms part at least one digital trunk to a standard different to that normally applicable to the digital trunks associated with the switching center. Each adapter terminal unit, equipped with a microprocessor-based control circuit, is connected by a switching matrix to the input/output lines of the switching center's switching matrix. It further comprises a data and signaling transfer device connected to the switching matrix and to a transmitter device and to a receiver device, one at the end of a transmit multiplex link and the other at the end of a receive multiplex link of the digital trunk. In this way the standard changes necessary for exchanges between the digital trunk and the switching center are effected.

Abstract: A digital switching network in an exchange having distributed control and a central switching network, the switching network comprising a plurality of independent planes, each of which is connected via inlet and outlet multiplex links to terminal units which include means for connecting terminals to said multiplex links, wherein each plane comprises synchronized switches (CX1) each equipped with a marker (MQ1) and constituting a single switching stage, the switches being connected in parallel to the inlet links (LE) of the plane, and each switch serving a respective group of the outlet links (LS), each multiplex link serving a group of terminal units (UT) in parallel, with each group of terminal units being connected to each plane of the switching network by at least one multiplex link, each switch being modular and including a control memory circuit driven by the associated marker (MQ), and a plurality of buffer memory circuits constituting square switching matrices, each of said square switching matrices be

Abstract: Subscribers (Ab1 to Ab8) in a telecommunications system are normally connected via respective subscriber lines (L1 to L8) to respective subscriber terminals (T1 to T8). Automatic subscriber line test means are connected via a subscriber line test bus (BL) and various relay contacts (r1 to r8 and re1 to re8) to the subscriber lines for testing purposes. Eight subscriber terminals (T1 to T8) populate a single circuit card, thereby constituting a terminal unit (TU1 to TUp). A group of terminal units is associated with a spare terminal unit (TUS). When a faulty terminal unit is detected, it is taken out of service and the spare terminal unit takes over. This is done by switching the subscriber lines connected to the faulty terminal unit over to the test bus. The spare terminal unit is likewise connected to the test bus. To enable the test means to continue testing the remainder of the telecommunications system without being interrupted by the emergency connection via the test bus, isolator means (I) are provided.