. Bell telephone magazine . ^•oS. Figure 3. Early Type of Transmission MeasuringSet Using 1000 Cycle Current with Ear BalanceMeasurements. Figure 5. Modern Trans-mission Testboard for Use inToll Offices, Showing theTransmission Measuring SetIN the Lower Left Panel, theAssociated Oscillator and Am-plifier IN the Center PanelAND AN Impedance Bridge inTHE Lower Right Figure 4. Portaum Mix^iKiNo Set Em PLOYING an .\.MPL1FIER AND MeTER. SHOWING THE Set in Use for Testing SwitchboardCircuits. Figure 6. Experimental Model of .Au-tomatic Recording Transmission MeasuringSet Arranged to Iroduce
. Bell telephone magazine . ^•oS. Figure 3. Early Type of Transmission MeasuringSet Using 1000 Cycle Current with Ear BalanceMeasurements. Figure 5. Modern Trans-mission Testboard for Use inToll Offices, Showing theTransmission Measuring SetIN the Lower Left Panel, theAssociated Oscillator and Am-plifier IN the Center PanelAND AN Impedance Bridge inTHE Lower Right Figure 4. Portaum Mix^iKiNo Set Em PLOYING an .\.MPL1FIER AND MeTER. SHOWING THE Set in Use for Testing SwitchboardCircuits. Figure 6. Experimental Model of .Au-tomatic Recording Transmission MeasuringSet Arranged to Iroduce a GraphicalRecord of Transmission Efficiency as aFunction of Frequency or of Time. SEVERAL TYPES OF TRANSMISSION ME.\SURING SETS THE TALKING EFFICIENCY OF TELEPHONE CIRCUITS ponent, thus greatly simplifying a very complex problem. Thefrequency used for this purpose is 1,000 cycles. Although the theory of transmission of single frequency cur-rents, as applying to telephone circuits, has now been highlydeveloped, it would be quite out of the question to make aprecise computation in each case of the efficiency for even onefrequency, such as thousand cycles. For practical telephonework it has been necessary to develop methods of approxima-tion and simplification and to prepare by these methods tablesand curves from which an approximate answer can be quicklyobtained in
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Keywords: ., bookauthoramerican, bookcentury1900, bookdecade1920, bookyear1922
