426,558. Electric selective signalling systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, and BROOME, J. H., 80, Leyland Road, Lee, both in London. Oct. 2, 1933, Nos. 27070/33 and 6096/34. [Class 40 (i)] In an indicating system, such as a train arrival or departure indicating system, in which certain of the matter to be displayed is normally invariable (e.g. the stations at which a train calls and the time it is due) whilst other matter is normally variable, (e.g. the platform number and the time late), the normally invariable information is displayed on a panel as the result of an operation indicative of the train rather than of the information to be displayed whilst the normally variable information is displayed as the result of operations specific to the several variable particulars. If the normally invariable information requires for its display more than one panel, the apparatus is arranged to select the required number of free consecutive panels and in such cases when variable information is set on the first selected panel, the information is automatically set on the remaining panels of the display. A miniatureindicator-board is provided at the control position. The invariable information can be controlled from a keyboard, by perforated cards or by a clock, and for special displays this information can be selected item by item. The invention is described as applied to a train arrival indicator as shown in Fig. 1. The normally invariable information comprises the time due and the stations from which the train is coming, which are displayed on slats A, B, C, D, &c., whilst the variable information comprises the platform number, the minutes late and the particulars of parts, e.g. 2 PARTS, PART 2. Each scheduled train has a number and to display the invariable information of a train self-locking tens and units keys TTK, TUK (or a units key only) corresponding to the number are depressed. A key DK relative to the day of the week has already been operated. A fifty-point uniselector such as TA50 in whose banks the train number keys have marked contacts, hunts for the markings and when the marked contacts are found, other wipers of the switch mark banks of switches such as IHI corresponding to the invariable particulars. The marking is effected through a translation frame, and is effective only if the translation is also marked by the day key indicating that the train runs on that day. A free display panel such as PANEL P1 is selected by means of a chain circuit passing through off normal wipers such as IH1 of indicator drum switches on engaged panels and clutches such as ISSC to drive the indicator drums of all the invariable display units are energized. The indicator drums, which may be similar to those described in Specification 357,616, rotate until wipers, rotated with the drums and passing over the banks marked through the translation field, engage the marked contacts when rotation stops. When all the rotating elements have been arrested, a series circuit is completed to key releasing magnets which release the operated keys. Lamps on a miniature indicator at the control point indicate the panel used and the display. To set up the variable information keys such as PTK, are operated corresponding to each unit of information, e.g. Parts key controlling display 2 parts part 2, Platform key No. 6 and minutes late units key No. 7, and then the key such as PAK corresponding to the panel on which the information is to be displayed is depressed. This key locks out all other keys and selects the relays, clutches and wipers corresponding to the indicators to be altered on the panels concerned. The indicator drums are turned until wipers carried by the drums find contacts marked by the depressed keys. When all the selected drums have been moved to their required positions, the depressed keys are released. The variable information may be displayed at the same time as the invariable information if the variable display control keys are depressed before the train number key is operated. If information regarding a non-scheduled train is to be displayed keys corresponding to each unit of the information must be operated followed by the depression of a special key SPK which initiates the selection of a free panel and the display of the selected information. If a scheduled train requires two or more panels for the display of its information, the apparatus selects a free panel only if adjacent panels, to the number required, are also free and then the indicators on the two or more panels are set consecutively. When variable information is to be set, the first panel only is selected and the apparatus tests adjacent panels, and if these are displaying particulars of the same train, the variable information is also set on these adjacent panels. Similarly if the information is to be removed from the display, the blackout key is operated followed by the key corresponding to the first panel of the group only, and the indicators of all panels displaying information regarding that train will be restored to blank positions. The station name units may be of the eleven slat type or of the two faced type and the station names may be different in different divisions of panels. In this latter case when a display is initiated, the apparatus selects panels in the correct division. An alarm is given if no day-key or more than one day key is operated. Display of the invarable particulars may be initiated automatically at predetermined times by clock CL. Instead of providing a translating frame, the normally invariable particulars may be selected by means of a perforated card which is pressed into contact with suitably spaced plungers. In such an arrangement the card is inserted in a box the lid of which is held locked electrically until all apparatus controlled by the operated plungers has been completely set. When hours and units minutes are to be displayed, the units minutes keys are operated, but the display is effected on the tens-minutes drum. Circuits for operating the apparatus are described in the Specification.