T1 carrier provides 24 voice channels by time division multiplexing and pulse code modulation (PCM). Each voice channel is sampled 8000 times a second and each sample is coded into a 7‐digit binary word. Provision for signaling and synchronization raises the pulse repetition rate on the repeatered line to 1.544 × 106 pulse positions per second. The bipolar pulse train out of the terminals is transmitted over pulp, paper or plastic insulated paired cables by the use of regenerative repeaters. For 22‐gauge cable pairs, repeaters are normally located at 6000‐foot intervals. The system has been designed for low cost and is being widely applied on many trunks interconnecting switching units within metropolitan areas. Western Electric Company manufacture of T1 begain 1962 and about 100,000 channels are now in service throughout the Bell System.

even though the Sr La line is on the long wavelength side of the Si K edge. In the case of the Si target the intensity of the continuous radiation relative to the Ka line is much less (lower atomic number) and the extrapolated values of the widths and percent reflections were more successful and served to increase confidence in the measurements made with the feeble radiation at the allowed voltage. Even so, the experimental error at this wavelength is considerably greater than in the data taken at the shorter wavelengths.The voltages in this work. were read with an accurate microammeter in series with a three megohm wire-wound resistance. CONCLUSIONSThe principal advantage for x-ray spectrometry of quartz crystals cut parallel to the (10· 0) planes lies in the relatively large grating space, making the crystals applicable to studies of wavelength in the range of 5 to SA. This range has been limited to single crystal spectrometers and spectrographs. At the large Bragg angles of this range the single crystal instrument can ea"sily be operated under conditions of resolving power in which the crystal diffraction pattern is the limiting factor, that is to say, in which the effect of the geometry of the arrangement of slits is negligible. As seen from the last column of Table I the resolving power of these quartz crystals is greater than that of calcite crystals for X> 3A.A second objective of this study is in obtaining data on a second set of grating planes of supposedly "perfect" quartz for use in checking the theories of crystalline reflection. Good agreement has been obtained between the Darwin-Ewald-Prins theory and experimental values for "perfect" calcite crystals. The theoretical values for quartz have not yet been determined because of incomplete knowledge of the crystal structure.

The microphonic response of different types of vacuum tubes to the same mechanical agitation covers a 70 db range of levels. Tubes of the same type, on the average, cover a range of about 30 db. These response levels are too sensitive to minute variations in testing conditions to be measurable with any great precision, but values which are reproducible to within 5 db are obtainable with a laboratory test set comprising a vibrating hammer agitator, a calibrated amplifier, and a thermocouple galvanometer indicator. Sputter noise is made measurable by frequency discrimination methods. Minimum microphonic disturbance under given service conditions is attained by using the less microphonic types of tubes which are available, by selecting the quieter tubes of a given type for use in positions sensitive to mechanical disturbance, and by protecting the tubes from mechanical and acoustic vibration. Examples of quiet triodes are the Western Electric No. 264B (filament) and No. 262A (indirectly heated cathode). Indirectly heated cathode type tubes are intrinsically less microphonic than filamentary types. Further microphonic improvement in the tubes themselves is made difficult by requirements for favorable electrical characteristics. Well designed cushion sockets can reduce microphonic levels by as much as 30 db, and other methods of cushioning, more expensive and less compact, can extend the reduction even farther. Sputter noise can be eliminated almost entirely in most types of tubes by commonly applied design features and manufacturing methods.

With the rapid expansion of broad‐band carrier telephone systems throughout the country, the use of these facilities for program transmission has become desirable. This paper describes a carrier program system capable of transmitting a band up to about 8000 cycles wide.