In that case all the current generated in all the cells join and flow along in one stream, from one end of the battery to the other. But now, all the positive plates may be connected together with one wire, and all the negative plates may be connected together with another wire, so that these two wires will thus be parallel with each other, and the lead wires which go to the motor are attached to these two parallel wires, and would represent the parallel type of connection. But it is the most common practice to divide the cell into two sets, each of which is called a _unit_. Each unit, having a certain number of cells, can also have them connected up in series, or in parallel, and the different parallel units may be connected up together, so as to form a connection which is in _multiple_ or in _series multiple_. Suppose there are eight units, each of ten volts, the motor would receive eighty volts. But now, if the cells are in parallel, or in multiple, as the case may be, then the pressure at the motor is equal to that of a single unit, but the current flow is eight times that of the foregoing example. The object, therefore, is to change the battery pressure on the one hand, and to produce the most effective action on the other hand, at the motor, and to do so make both battery and motor more efficient. THE CONTROLLER.--The device which performs this operation, at the will of the operator, is called the _Controller_, which changes the wiring connection from series to multiple, or the reverse. The Controller is, in all probability, the most complicated piece of mechanism in the entire electric car. It must make an entire series of changes for each of the different speeds, of which there are frequently six. The fields of the motor are also connected in series, or both series and multiple, so as to give a still greater efficiency. By this means the terminal points of the Controller may be turned, (1), so they will connect the batteries in multiple and the field windings in series; or, (2), the batteries in multiple and the fields in series multiple; or, (3), the batteries in series and the fields in series; or, (4), the batteries in series and the fields in multiple. The figures in parentheses indicate the first, second, third and fourth speeds, respectively, and in such an arrangement two battery units are used, and also two motors. The same rule as to efficiency applies with one motor, and two or more battery units. The battery unit may be of any desired number of cells, as stated. THE GENERAL EQUIPMENT.--Cars for pleasure purposes are of different types, such as runabouts, roadsters, victorias, coupés, broughams, and the like, provided with batteries which will permit runs of at least 100 miles on each charge. SPEEDS.--The Controller will permit of speeds ranging from five to thirty miles an hour. The number of cells vary with different makes, from twenty to forty, and the number of plates in each cell average about fifteen.