Abstracts of Technical Articles from Bell System Sources (01 October 1939)

Proc. American Wood-Preservers' Association, Electrochemical Society Preprint 76-25. Electrochemical Society Preprint 76-24. 742 1939. ABSTRACTS OF TECHNICAL ARTICLES 743 one-year outdoor exposure test. Such differences as were found were shown to be due either to deterioration or improvement in the paint film as the result of weathering. Characteristics of Modern Microphones for Sound Recording.4 F. L. HOPPER. Factors influencing the choice of a microphone for sound recording are considered. The characteristics of a new miniature condenser transmitter and amplifier, as well as a number of other types of microphones now in use, are included. Cold-Cathode Gas-Filled Tubes as Circuit Elements.5 S. B . INGRAM. 

The application of electronic devices to the local systems plant is still in its infancy. One of the first of these devices to receive extensive use is the cold-cathode gas-filled tube. As a sensitive relay it is beginning to make its appearance in a number of telephone control and signaling circuits, being best known for its use in the standard four-party subscriber set where its rectifying property enables it to discriminate between positive and negative polarity for selective ringing. Compared with other types of vacuum tubes the coldcathode tube has the advantages that it operates without cathode heating power, has the ability to start immediately when a signal is applied, and does not deteriorate when not passing current. These advantages make it particularly suitable for use in telephone circuits where intermittent service is common and long life and economical operation are required.