13,174. Herzog, F. B. June 24. Indicators or annunciators.-Relates partly to improvements on the electrolytic annunciators described in Specification No. 1301, A.D. 1898, and more generally to the combined use of such annunciators, which give a transient indication, with others of the electromagnetic type, in which the indication continues until the apparatus is re-set by some manual operation. This combination is applicable for telephone central apparatus, and the electrolytic annunciator of each line may be connected either in series or in parallel with the corresponding electromagnetic annunciator. In the electrolytic annunciator shown in Fig. 1, the electrodes F<1> are mounted in a hollow base 32, preferably of opal glass, which is immersed in a solution of potassium iodide &c. contained in the jar 40. The jar is connected to the base by the screw or other cap 42, with a washer 34 interposed between them, and the base is hung, by the pin 15 on the elbow-piece 17, 18, from the arm 4 of the support 1, so that the jar, which is normally held against the support by a screw 8 &c., can be swung outwards, as shown, for inspection or repair of the parts &c. The support is adapted to be fixed to a table or wall &c., and the wires 55 from the electrodes are connected to the leading-in wires 56 through the junction-board 53. The single negative electrode K<1> is connected to the common return wire 62, 65. The wire from each electrode passes through a soft rubber plug in the wall of the base. By providing a convexed backing J<111>, of vulcanite or hard rubber, for each electrode, the electrodes can be made of platinum foil. In the arrangement shown, a tube 28, 29<1> connected to an elastic bulb 25<1> is provided for blowing air through the electrolyte to remove the indications, the bulb being formed with a number of perforations to prevent backward suction. A vent tube 70 is provided for the escape of the air from the jar. A wire 6<1>, Fig. 2, projecting out from below and extending upwards between the electrodes F<1>, may be substituted for the negative electrode K<1>. The base 32 is filled up with a cement preferably of wax and resin, to protect the wires &c. The indications may be placed on a plate 30, mounted on the base, preferably to read alternately with the electrodes on either side, as shown in Fig. 2. To aid in retaining the iodine stain on the electrodes, and to protect it from gas bubbles &c., the electrodes may be set in recesses in the base, as shown in Fig. 5, or in suitable perforations in a separate plate 78, as shown in Fig. 4. Instead of effecting the indications by a stain of iodine &c., they may be given by the appearance of gas bubbles on a black background, which may be formed of black silk &c. arranged to cover the electrodes either singly or collectively. In this case, the electrolyte may consist of a saline solution &c. containing gum arabic. Instead of employing the air blower, the jar may be mounted so that it can be lifted up and shaken, to dissipate the stain &c. The base 32 may also be replaced by somewhat different arrangements.