Abstracts of Technical Articles by Bell System Authors (01 July 1944)

F. F. SHIPLEY. A new crossbar toll switching system was placed in service in Philadelphia in August 1943. Important improvements offered by this system include: 1. Transmission objectives are met more readily and substantial economies are obtained in outside plant and in repeater equipment. 2. Extended use of toll dialing results in operating economies and improved service to subscribers. Calls over circuits still on a ringdown basis are also handled more expeditiously and with operating economies. 3. Flexibility due to the use of sender and markers to control establishing connections will be useful in meeting future toll switching requirements. 

Low-Frequency Quartz-Crystal Cuts having Low Temperature Coefficients.2 W. P. MASON AND R. A. SYKES. This paper discusses low-frequency, low temperature-coefficient crystals which are suitable for use in filters and oscillators in the frequency range from 4 to 100 kilocycles. Two new cuts, the MT and NT, are described. These are related to the +5-degree AT-cut crystal, which is the quartz crystal having the lowest temperature coefficient for any orientation of a bar cut from the natural crystal. When the width of the +5-degree X-cut crystal approaches in value the length, the motion has a shear component, and this introduces a negative temperature coefficient which causes the temperature coefficient of the crystal to become increasingly negative as the ratio of width to length increases. The MT crystal has its length along nearly the same axis as the -f 5-degree X-cut crystal, but its major surface is rotated by 35 to 50 degrees around the length axis.