The heart of the chaine (or connection network)

Summary form only given. This ensemble replaces the rotary, crossbar type, spatial switching systems. In earlier days, these formed the bigger part of an exchange. With temporal switching, the number of chips has been considerably reduced. Considering that the natural support of speech signal is the "P.CM. time slot", the "switch" is a mixer of coded pulse trains which works as follows : it does an "application" (in the mathematical sense of the word) of the time intervals of 8 entering pulses (coded by P.CM.) to the time intervals of 8 outgoing pulses (coded by P.CM.). This appli cation follows a law that is already stored in the memory and which is modified only at the time of establishment or at the end of a telephone call. This represents an L.S.I, circuit using more than 30.000 transistors and working as a switch of 8 x 30 x 64 = 15 Mbits / second.