256 BELL SYSTEM TECHNICAL JOURNAL 



chronous vibrating relay would be beyond the scope of this paper 

 but the way in which it permits an advantage in speed of operation 

 may readily be appreciated from a consideration of the signals shown 

 in Fig. 11. 



Consider first the conditions in plain relay operation without the 

 use of the vibrating relay principle. The signal train A, Fig. 11, 

 represents the word "western" as translated into the code used in 

 the multiplex printing telegraph system. If this word is transmitted 

 over the combined cable and distortion-correcting networks at a 

 suitable speed for plain relay operation, it will be received in the 

 form, B, in which a t'-ansmitted impulse of unit length has resulted 

 in a received impulse of about the same amplitude as that of impulses 

 two or more units long. A simple relay operated by the signal train, 



B, will substantially reproduce the original transmitted train, A. 

 Consider now the signal train, C, in which the same word "western" 



is transmitted at twice the speed of A. With the same adjustment of 

 cable and terminal networks it will be received in the form, D, in 

 which impulses of two units of length are received with the same 

 amplitude as that with which the unit length impulse was received 

 in B, whereas the amplitude of a succession of received reversals of 

 unit length in D is reduced nearly to zero. Obviously, if D were 

 applied to a simple relay, it would not cause the original signal train, 



C, to be reproduced. However, C can be reproduced from D by 

 means of the synchronous vibrating relay which is arranged to supply 

 impulses of unit length locally, unless prohibited from so doing by 

 currents due to impulses of two or more units of length. One may 

 regard the cable and terminal networks as converting the transmitted 

 two-element (plus and minus) signals into three-element (plus, zero 

 and minus) signals which the vibrating relay reconverts into two- 

 element signals, and in this way permits operation at a speed which 

 is much higher than is possible with a plain relay. With the Gulstad 

 relay or with minor modifications of it, the locally interpolated im- 

 pulses are supplied from a local vibrating circuit and do not always 

 occur at exactly the right time to be most effective. With the 

 synchronous vibrating relay, these impulses are controlled by the 

 distributor and are therefore introduced at precisely the right time. 

 It is interesting to note that this can be done in a system in which the 

 incoming signals control the rate of the distributor. 



Another feature of the apparatus for the loaded cable is its high 

 degree of precision and refinement. The cost of a cable relative to 

 that of even the most refined apparatus is so great that no considerable 

 sacrifice of speed can be justified by ordinary economies in apparatus. 



