A printed circuit board includes at least one code establishing section which is readily removable or separated from the board and also includes printed wiring connected to a voltage source and to a ground. When the code establishing section is removed, the level of an output signal from the voltage source is inverted from the level of the output signal prior to removal of the code establishing section in order to establish a desired unique code. A second arrangement of the apparatus includes a main portion and two removable portions of the board with a pair of voltage sources on the main portion and a ground connection on one of the two removable portions. The method of establishing a unique address code is accomplished by removing one of the removable portions to provide an output signal of a level that is inverted from the level of an original signal. Subsequent removal of the other removable portion provides an output signal of a level that is the same level as the original signal.