Neutralization of telegraph crossfire

With the simple means here described for neutralizing mutual interference between parallel telegraph circuits, it has been found practicable to effect a reduction to 10 or 20 per cent of the original values. This has improved considerably the operation of some circuits and made available others which were previously unsuitable. The resulting improvement in transmission has made possible the elimination of certain intermediate telegraph repeaters with material savings. The neutralizing apparatus has no material effect when crossfire is not present, that is, when the paralleling wires are idle. It has been found that the use of arrangements here described on certain long open wire circuits makes possible fast manual full-duplex operation where only medium-speed half-duplex operation was possible before. Furthermore, in the case of some cable circuits where it was impossible to operate more than two telegraph circuits per quad, it is now practicable to obtain four telegraph circuits.