Modern Single-Sideband Equipment of the Netherlands Postals Telephone and Telegraph

After we introduction, a short description is given of the equipment developed before 1940, followed by a survey of the principles of the modern equipment. The way in which the automatic tuning in the receiver in accomplished is described in detail. A summary is given of the advantages of the modern equipment with respect to the earlier art. In an appendix, some theoretical considerations are given with respect to the automatic tuning control; particularly, the conditions for a stable circuit are derived.