it to
the battery. If two bulbs are used, as shown ill Figure 51, each half
of the alternating current wave is used in charging the battery. To
trace the current through this rectifier assume an instant when line
wire C is positive. Current will then flow to the graphite electrode
of tube A, through the secondary winding of the transformer S to the
center tap, through the rheostat, to the positive battery terminal,
through the battery to the center of the primary transformer winding
P, and through part of the primary winding to D. When D is positive,
current will flow through tube B from the graphite electrode to the
filament, to the center of transformer winding S, through the rheostat
and battery to the center of transformer winding P, and through part
of this winding to line wire C. In the actual rectifiers the rheostat
shown in Figures 50 and 51 are not used, regulation being obtained
entirely by means of other windings.

From the foregoing description it will be seen that if the alternating
current supply should fail, the batteries cannot discharge into the
line, because in order to do so, they would have to heat up the
filament and send current through the bulb from the filament to the
graphite electrode. This the batteries cannot do, because the
connections are such that the battery cannot send a current through
the complete filament circuit and because, even if the batteries could
heat the filament they could not send a current from the filament to
the graphite, since current cannot flow in this direction.

As soon as the alternating line is made alive again, the batteries
will automatically start charging again. For these reasons night
charging with the Tungar is entirely feasible, and no attendant is
required to watch the batteries during the night. The Tungar Rectifier
is made in the following sizes:

A. Two Ampere Rectifier

Catalogue No. 195529

[Fig. 52. The Two Ampere Tungar Rectifier]

[Fig. 53 Internal wiring of the two ampere tungar rectifier]

This is the smallest Tungar made. Figure 52 shows the complete
rectifier. Figure 53 shows the internal wiring. This Tungar will
charge a 6 volt battery at two amperes, a 12 volt battery at one
ampere and eight cells at 0.75 ampere. It is suitable for charging a
lighting battery, or for a quick charge of a motorcycle or ignition
battery. It will also give a fairly good charge over night to a
starting battery. Another use for this rectifier is to