An improved detached-contact-type of schematic circuit drawing

THE ever-increasing complexity of telephone and telegraph switching circuitry in the Bell System reached a stage, about 10 years ago, where many of the conventional type of schematic circuit drawings presented difficulties in training of personnel and maintenance. It then became necessary, for the more complex circuits, to prepare and maintain a separate series of drawings especially streamlined for training purposes and for aiding maintenance. However, the preparation of two sets of drawings for these cases and the necessity for keeping them in step as improvements and changes were added was costly. To meet this problem the new type of circuit drawing described in this paper was developed. It is designed for easy understanding and incorporates in a single package the basic circuit information required for manufacture, installation, training, maintenance, and engineering analysis.