Abstract: A coupling system for a telecommunication exchange installation is described having a plurality of interconnected binary switching matrices. Each switching matrix has at least two row and two column lines with means for connecting row lines to column lines. A plurality of connection lines form input and output lines for the system of interconnected switching matrix. The interconnection arrangement for the interconnected switching matrices is such that a row line of at least one multiple is connected to a row line of another multiple or a connection line. The other row line of the one switching matrix is connected to a column line of another switching matrix or to a connection line. One column line of the one switching matrix is connected to a column line of another switching matrix or to a connection line. The other column line of the one switching matrix is connected to a row line of another switching matrix or to a connection line.

Abstract: An R-2R-ladder network has n chained ladder cells, each controlled by an associated one of n control circuits wherein n corresponds to the number of digits of a digital signal to be converted. Each cell is composed of a series transistor inserted between two neighboring nodes of the ladder network and of a first, a second and a third cross transistor. The cross transistors are commonly connected by one main electrode to form a star circuit. The first, second and third cross transistors are connected by a second main electrode to the node of the cell, to a sum current output line and to ground, respectively. The gates of the series transistor and of the first cross transistor are directly connected to a reference voltage source whereas the gates of the second and the third cross transistor of each ladder cell are connected to a respective one of two signal outputs of the associated control circuit.