. The Bell System technical journal . value. For offices where the frequency of the commercial supply is suffi-ciently stable, an additional and somewhat more convenient methodfor checking the speed has been made available. It consists of aspecial target mounted on the generator shaft, which is illuminated bya neon lamp associated with a wave-shaping circuit which makes theflashing time a very brief portion of each pulse of the 60-cycle other words, the attendant in this case looks at the target constantlyunder intermittent illumination, while in the former case he views itintermitt
. The Bell System technical journal . value. For offices where the frequency of the commercial supply is suffi-ciently stable, an additional and somewhat more convenient methodfor checking the speed has been made available. It consists of aspecial target mounted on the generator shaft, which is illuminated bya neon lamp associated with a wave-shaping circuit which makes theflashing time a very brief portion of each pulse of the 60-cycle other words, the attendant in this case looks at the target constantlyunder intermittent illumination, while in the former case he views itintermittently under constant illumination. Testing FacilitiesWhile developments in carrier telegraph equipment have resulted inconsiderable economies, the ever increasing demand for service whichis freer from errors and interruptions and is adaptable to circuits ofgreater length and complexity has tended to render the maintenanceproblem increasingly difficult and time consuming. Voice-frequency ADVANCES IN CARRIER TELEGRAPH TRANSMISSION 197. Fig. 21—Carrier-telegraph test set. General view. 198 BELL SYSTEM TECHNICAL JOURNAL telegraph circuits equipped with level compensators must be subjectedto a series of specialized tests and adjustments whenever placed inservice and at periodic intervals thereafter. To provide for this, aspecial testing set comprising in readily available form all the testequipment required for this purpose, has recently been includes the following features: 1. Bias measuring circuit. 2. Filament-activity test-circuit and filament-current measuring circuit. 3. Drift measuring circuit. 4. Test amplifier. 5. Adjustable attenuator. With this set all terminal tests may be made from one end of thecircuit without the use of a line or external line-simulating repeater as
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
