A New Single Channel Carrier Telephone System*
H. J. Fisher, Milton L. Almquist, R. H. Mills · Bell System Technical Journal · 1938
The single channel carrier telephone system described in the following paper is designated the Type H. It is characterized by several new features, making it applicable not only to the needs of telephone companies but also to those of railroads, power systems and oil companies. It replaces the Type D single channel carrier system, more than 500 of which are now in operation in the Bell System, and, in addition because of its lower cost is applicable to shorter distances. It therefore marks another step in extending the use of carrier. Reduction in size and provision for operating on a-c supply simplify its installation, and its portability makes it well suited to provide emergency circuits.