Miscellany

IN the July, 1930, issue of the Experimenter., Horatio W. Lamson described an instrument called the cardiotachometer which he built in collaboration with Paul Bauer, for measurement of a patient's heart at rest or during exercise. Two of our readers have written that a similar instrument was described by l> r. Ernst P. Boas in the Archives of internal Medicine for March, 1928. Mr. Lamson did not then know of Dr. Boas' cardiotachometer or lie would have referred to it, inasmuch as it had many...

Electrical Communications Technique And Its Applications In Allied Fields

NSTRUMENTS for the measurement of audio frequencies are usually based on one of the numerous bridge circuits in which frequency enters explicitly. The familiar tuned-circuit wavemeter has not made a satisfactory audio-frequency meter because of the large amount of power lost in it when the usual current indicator is used. The resonance bridge makes use of a similar tuned circuit in one arm, the other arms being pure resistance. For any reasonable values of inductance the capacitance required to...

Beat Frequency oscillators

THE distinguishing characteristic of the heat-frequency type of oscillator is a wide range of output frequency with a small variation in circuit constants. The output of the beat-frequency oscillator is, with proper design, substantially constant in voltage over the range for which the instrument is designed. An instrument of these characteristics has a number of applications in the fields of test and laboratory measuring equipment. It is particularly adapted to making rapid adjustments in...

Precision Frequency Measurements

SINCE early this year, the Bureau of Standards has been sending from WWV a wreekly high-precision standard-frequency schedule1 Editor, General Radio Experimenter. 1 Transmissions are at present being sent from 1 30 to 3 30 and from 8 00 to 10 00 p.m., Piastern Standard Time, every Tuesday except that week at a frequency of 5000.00 kilocycles per second 60 meters . usually the week of the 20th in which the regular monthly transmissions are scheduled. Complete schedules, field-intensity data, and...