On the Suppression of Induction Clamour in Telephones. 281 
Fig. 4. 
OD 
B 
A is the disturbing or telegraphic circuit, and B the telephonic 
circuit. It will be obvious that the secondary currents set up in the 
latter by the former will have equal and opposite effects upon the 
terminal Telephones, and this irrespective of how many inducing 
wires there may be juxtaposed. This, unquestionably, is a 
perfect correction, but the expense and increased resistance of 
the return line are serious obstacles to its general use, though it 
is, I believe, extensively adopted in United States telephonic lines, 
It was at this stage that Professor Hughes published an 
account of his induction balance, wherein he proposed to over- 
come the induction clamour by a compensating induction coil, 
very similar to the manner which we have seen Wilson and Edison 
had already invented. Hughes’ paper was read before the 
Society of Telegraph Engineers on March 12th, 1879. 
Fig. 5. 
Fig. 5 shows one of Hughes’ plans. A and B are two neigh- 
bouring lines; between each line and its receiving instrument R a 
coil of wire C C’' is inserted, the length of the wire in each coil 
being proportioned to the length of the line, and the distance of 
the coils apart being adjusted to the relative distance of the lines. 
By winding the wire in coil C in the opposite direction to that 
in C’ a contrary induction to that produced between the two 
straight lines is set up, and thus the line disturbance produced 
by A upon B may be effectually neutralized ; iron cores may 
