Carrier Application to a telegraph plant

THE REQUIREMENTS for carrier systems in telegraph plants differ somewhat from those in telephone plants. Primarily these differences are due to the fact that telegraph plants are based upon the wide use of d-c. telegraph circuits which can be operated fairly successfully on a ground return basis. Furthermore, the operating energy levels of the various circuits on the same lead are not restricted by the presence of other types of communication circuits occupying a frequency transmission range other than that required for d-c. telegraph signals. Other equally important factors enter into the problem, and are outlined in this paper.