This is a bill in equity for an injunction to restrain the alleged infringement of letters patent No. 140,536 for an improvement in circuits for electric railroad signals, issued July 1, 1873, to Frank L. Pope, of whom the appellants, who were complainants below, are assignees. On final hearing the bill was dismissed by a decree now brought here for review by this appeal. The drawing which accompanies and illustrates the patent is as follows:
The following is the substantial part of the specification, together with the claims: 'My invention consists in a peculiar arrangement of electric circuits, in combination with a battery, and with two or more circuit-closers operated by moving trains or otherwise, whereby a series of two or more visual or audible signals, situated at intervals along the line of a railroad, may be operated by currents of electricity derived from a single barrery, thereby obviating the inconvenience and expense of employing, as heretofore, one or more separate batteries situated at or near each signal for the purpose of actuating the same.
'In the accompanying drawing, A, A, represents a portion of the track of a railroad. At intervals of, say, a mile, more or less, sections of the said track, a, a 1 insulated from the remainder in a manner well understood, and therefore requiring no detailed description. B is a galvanic battery, of any suitable construction, and placed in any convenient location near the line of the railroad. Two wires or other conductors, C and Z, are attached to the positive and negative poles, respectively, of the battery, B, and extended to any required distance in a direction parallel or nearly so to the line of the railroad. The conductors, C and Z, may be placed on poles, and should be suitably insulated from each other and from the earth. The conductors, C and Z, are virtually prolongations of the positive and negative poles of the battery, B. Each of the insulated sections of track, a, a 1 point at or near which it is desired to erect a signal, and any required number of these may be employed to meet the requirements of any particular case. M, M1, and M2 are the electro-magnets, which actuate or display the respective signals. The said signals may be of any suitable construction, and should be provided with some suitable means of retaining them in position or action after the circuit through the magnets, M, M1, or M2, has been interrupted. m, m1, and m2 are magnets so arranged as to release, reverse, or stop the action of said signals, which have previously been brought into action by the magnets, M, M1, and M2.
'The operation of the apparatus is as follows: Suppose a train moving along the track, A, A, from left to right in a direction indicated by the arrow. Upon reaching the point, a, the wheels and axles of the train will form an electrical connection between the opposite insulated rails, and a circuit will be formed between the conductor, C, and the conductor, Z, traversing wires, 1 and 2, magnet, M, and wire, 3, and the signal attached to M will consequently be displayed. Upon the arrival of the train at a1 the same operation will be repeated, and another connection formed between C and Z, traversing the wires, 4 and 5, magnet, M1, and wire, 6, while at the same time a portion of the current will traverse the branch-wire, 7, magnet, m, and wire, 8. Thus the signal attached to M1 will be act ated, and simultaneously the action of the magnet, m, will release or reverse the action of the first-mentioned signal. Upon reaching the point, a2, the closing of the circuit by the train will, in like manner, cause the signal attached to M2 to be displayed, and the signal last displayed by M1 to be withdrawn. In this manner any required number of such signals may be operated by means of a single battery.
'The respective resistance of the several circuits should be so adjusted that they will be as nearly as possible equal to each other, as a much more perfect action of the apparatus will be secured thereby.