CONTROLLING "B" ELIMINATOR AND "A" BATTERY TRICKLE-CHARGER

Radio Record, Volume I, Issue 37, 30 March 1928, Page 13

CONTROLLING "B" ELIMINATOR AND "A" BATTERY TRICKLE-CHARGER

Tt is quite easy to control a receiver ‘with B eliminator aud A battery trickle-charger with a single donblepole double-throw switch, so that in one position the receiver and eliminator are both ent out from battery and mains, and the trickle-charyer is switched on to charge the A battery, and in the other position the trickle-charger is cut out, power connected to the elimina. |

tor, and the receiver filaments switched on, provided, of course, that low tension controls on the receiver are: left in position for reception. In order that the valve filaments may switch on before and off after the eliminator, 1 is only necessary to make

the A battery contact «en the switch higher than the opposite one of the pair. IMPEDANCE. MPEDANCEK is influenced by frequency, as is reactance, and concerns direct as well as alternating currents, as does resistance Like resiatance, it is measured in ohms, the number of ohms heing the number of volts reyjuired per ampere of current. Vor example, the resistance of a pair of headphones is very often 4900 olimis. The impedance of such a pair to a cur: rent at a frequency of 800 cycles per second may be about 30,000 ohms, whereas to a current at 100 cycles, i: would be a little more than half that amount. We may summarise these re sults as follows: Resistance is the opposition offered flow of a current, and is a property of the cirenit or apparatus concerned, being independent of the nature or frequency of the current. Reactance is the opposition offered by an inductance or capacity to en alternating current. Only aliernating ot ehanging currents encounter reactance. the magnitude of which depends upon the frequency of the current, Impedance is the total opposition offered by a circuit, and is made up of resistance and reactaneé. Where direct current is concerned, the impedance ‘s the same as the resistance, for there is no reactance.