Electrical news and engineering . and closehis battery circuit, although a foot switch. Fig. 3, may alsobe employed for this purpose. Special instruments of lowimpedance give the dispatcher improved receiving efficiency. A special breast transmitterand 70-ohm head receiver arethe types in use. To meet the conditionspreviously outlined, a key orfoot switch is used, as shownin Fig. 2. The listening posi-tion gives current through thereceiver and condenser in ser-ies directly across the line andlirovides ideal receiving con-ditions. With the key thrown totalking position, the receiver isin series
Electrical news and engineering . and closehis battery circuit, although a foot switch. Fig. 3, may alsobe employed for this purpose. Special instruments of lowimpedance give the dispatcher improved receiving efficiency. A special breast transmitterand 70-ohm head receiver arethe types in use. To meet the conditionspreviously outlined, a key orfoot switch is used, as shownin Fig. 2. The listening posi-tion gives current through thereceiver and condenser in ser-ies directly across the line andlirovides ideal receiving con-ditions. With the key thrown totalking position, the receiver isin series with a retardationcoil—normally short circuited—and both are in parallel withthe secondary of the inductioncoil. These arc bridged acrossthrough the condenser. This gives the best possibleoiinditions for transmitting. The impedance of this bridgewhile receiving is ohms to talking current, nearly allof which is available for receiving. The retardation coil cutsdown excessive side tones in the receiver when talking, and. Fig. 3. the li 66 THE ELECTRICAL NliWS also Iiy llic iiniicdance of the receiver current forcesmore of the transmitter current on the line. Should thedispatcher wish to break in on the operator, sufficient ofhis voice currents will pass through the operators receiverand attract his attention. Here, too, special apparatus isused in induction coil, transmitter and high resistance re-ceiver. This arrangement is in use on circuits up to two hundredmiles and over, with as many as forty-live stations; of thisnumber twenty stations may be listening simultaneouslywithout seriously impairing the transmission on the system is in use by the C. P. R. and G. T. R., and inboth instances were supplied by the Northern Electric andManufacturing Company. C, P, R. Telephone Train Despatching Train despatching by telephone was the subject ofan address by Mr. W. J. Camp, electrical engineer of thetelegraph department of the C. P. R., at a noonday dinne
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Keywords: ., bo, bookcentury1800, bookdecade1890, bookidelectricalnewsen20donm
