GB207354A - Improvements in or relating to multiplex telegraph systems - Google Patents

Abstract

207,354. Automatic Telephone Manufacturing Co., Ltd., and Harrison, H. H. Oct. 28, 1922. Multiplex telegraphs; synchronous movements.-In a multiplex system using a code with signal units of unequal length, such as the land line Morse code, the line time is divided equally among the different channels during periods corresponding to the longest period (such as that of the dot) of which the periods of all the signal units are exact multiples. Figs. 3 and 4 show the distributing arrangements for a two-channel system at the transmitting and receiving stations respectively. Fig 1 represents at a and b the letters L and F sent simultaneously over the first and second channels respectively, and at c and d the polarity and duration of the currents sent to line in respect of each channel. In the transmitting distributor, Fig. 3, a contact brush arm CBA sweeps over contact rings R<1> and R<2>, the former being connected to a polarized transmitting relay TR, and the latter being divided into alternate segments a, b connected respectively through the normally closed contacts of the synchronizing switch SS to the transmitter T<1> and T<2>. The corresponding star wheels SW<1> and SW<2> are fixed to the shaft carrying the arm CBA<1>, and this shaft is driven by a phonic wheel or the like. The length of the segments a, b is such that four segments subtend an angle equal to the pitch of the star wheels, this arrangement resulting in the suppression of the second half of each signal component for the first channel, and of the first half of each signal component for the second channel. In the receiving distributor, Fig. 4, a brush arm CBA<1>, moving in synchronism with the arm CBA, sweeps over contact rings R<3> and R<4>, the former being connected to the polarized line relay LR, and the latter being divided into segments a, b connected alternately to polarized storing relays PR<1> and PR<2> controlling receiving apparatus RA<1> and RA<2> corresponding to the two channels. The arm CBA<1> is driven by a phonic wheel PW controlled by a Gulstad relay vibrator GR of which the correcting upper winding is traversed by a momentary current at each reverse of the line relay LR, the flow of continuous current being prevented by a condenser c<1>. The speed of vibration is initially adjusted by varying the values of resistances r<1>, r<2> and of a condenser c<2> when the switch SS is in position to connect positive and negative current alternately over the line, and phase adjustment is effected by rotating the divided ring or the brush arm. In a modification, the star-wheels are rigidly connected to ratchet wheels which have twice as many teeth as the star wheels and are stepped by magnets controlled by a second brush on the arm CBA connecting an earthed ring with a ring divided into segments equal in number to the segments of ring R<2>, these segments being alternately blank and connected to the magnets.