The Standard Electrical Dictionary

1. Universal Battery System

   A term in telegraphy. If several equal and high resistance telegraphic circuits are connected in parallel with each other from terminal to terminal of a battery of comparatively low resistance each circuit will receive the same current, and of practically the same strength as if only one circuit was connected. This is termed the universal battery system. It is a practical corollary of Ohm's law. The battery being of very low resistance compared to the lines the joining of several lines in parallel practically diminishes the total resistance of the circuit in proportion to their own number. Thus suppose a battery of ten ohms resistance and ten volts E. M. F. is working a single line of one hundred ohms resistance. The total resistance of the circuit is then one hundred and ten ohms. The total current of the circuit, all of which is received by the one line is 10/110 = .09 ampere, or 90 milliamperes. Now suppose that a second line of identical resistance is connected to the battery in parallel with the first. This reduces the external resistance to fifty ohms, giving a total resistance of the circuit of sixty ohms. The total current of the circuit, all of which is received by the two lines in equal parts, is 10/60 = .166 amperes. But this is equally divided between two lines, so that each one receives .083 ampere or 83 milliamperes; practically the same current as that given by the same battery to the single line. It will be seen that high line resistance and low battery resistance, relatively speaking, are required for the system. For this reason the storage battery is particularly available. The rule is that the resistance of the battery shall be less than the combined resistance of all the circuits worked by it.