(7.//.V or rii(^ n\iy rni.r.nioxr. Rr.i'r.irrRs 2\ 



I>i:viii;s K.MrioMM. \ou !■: (omkoi.i.i d Ki i.\\-^ 



Maiu' (iilTercnt ticvirvs .liiuinii to sriiin- llu- pr.ii-tiral (.•(|iii\.iU-iU of 

 t\vi)-way rcfKMter operation by moans of rulaxs (inri-li.inical or 

 ihcrinionic) rontrollcti by the voice currents tluMUselvcs have Inrn 

 suggestetl. In these devices the action of the rela\s is such that 

 when transmission is passing in one direction throiij;ii a reix-ater, 

 the transmission in the opposite direction is either wholly or par- 

 tially blocked. K\i(lently the gain of such a repeater as this is not 

 limited by impedance irregularities in the lines, since it is really a 

 one-way device during the passiige of speech currents. 



Repeaters controlled by voice operated devices will not be dis- 

 cussed here further in view of the fact that the principal object of 

 this paper is to treat repwater systems which are truly two-way in 

 their operation. 



Other Types of Repe.\tf.r That H.we Been Proposed 



Several of the arrangements that have been proposed by inventors 

 who sought unsuccessfully to produce two-way repeaters not subject 

 to limitation by line irregularities will now be described. 



1. Repeaters Involving Balance. A great many circuits ha\e been 

 devised which involve the principle of balance. These always in- 

 volve the same fundamental principle as the h\brid coil used in the 

 repeaters now in commercial service though often the arrangement 

 appears quite different. This principle is that the output energy 

 of the amplifier working in one direction, for example, the east bound 

 amplifier, is divided into two parts, one of which is sent into the line 

 east and the other into the corresponding network. The input 

 terminals of the west bound amplifier are so connected that the effect 

 on them of the current entering the line east is opposed by the effect 

 of the current entering the network and consequently the impedances 

 of the line and network must accurately balance each other to keep 

 the output energy of one amplifier out of the input circuit of the 

 other. Sometimes the balance is effected by connecting the line 

 and network into a common electrical circuit and connecting the 

 input terminals of the amplifier to two points of equal potential 

 in this circuit. In other arrangements two fluxes which depend 

 upon the currents entering the line and network are balanced against 

 each other in the core of a special transformer so that a winding 

 connected to the input of the amplifier is not affected. 



Usually the impedance of the network equals that of the line, but 

 arrangements are possible and even have certain advantages in 



