786,470. Speedometers; recording-apparatus. KIENZLE APPARATE GES. Jan. 13, 1956, No. 1233/56. Class 106 (3) and 106 (4). A tachograph for a motor vehicle comprises a device for indicating time and speed, another for mileage and means 4, 6, 5 for recording speed, mileage and rest or motion, clockwork 8 for driving the time indicators 10, 10<SP>1</SP> and record sheets 9 and additional devices for indicating and recording at least one of the following: gear change, operation of signalling arms, r.p.m. of the motor, torsional moment of the motor and the braking performance in the vehicle all contained in a housing 1 with a tiltable lid 2. The speedometer and clock hands 11, 10, 10<SP>1</SP>, the clockwork 8 and record disc 9, pivot 19, arm 13 and r.p.m. stylus 14a are all arranged in the lid 2; while the styli 4, 5, 6 for recording speed, rest or motion and mileage and the r.p.m. drive shaft 23 are all arranged in the casing. The shaft 23 drives the arm 13 through a releasable coupling and when released upon opening the lid the arm 13 is spring-urged against a stop so that the stylus 14a records a circular zero line which indicates the fact that the lid has been opened. Stationary but adjustable styli in the lid inscribe circles to indicate maximum and minimum desirable r.p.m. and coloured bands on the r.p.m. scale give a corresponding indication in co-operation with an r.p.m. index. Lamps 27, 28, 29, Fig. 9, give warnings when a predetermined speed is exceeded or the r.p.m. are outside a desired range, being arranged in parallel circuits including switches 34, 46, 49 which are closed by cams 35, 40, 39 at the respective speed limit and lower and upper limits of r.p.m. Cams 45, 48 driven at constant speed cause slow and rapid flickering of the lamps 28, 29 when the associated switch 46, 49 is closed. An alternative circuit, Fig. 8, not shown, is described for giving all these warnings with one lamp only. Similar circuits may be used for indicating when a gear change should take place by actuating the switches which light the lamps in dependence on the torsional moment or the motor output indirectly from the position of the regulating levers or from the pressure in the suction line. Among the auxiliary factors, recorded in special areas on the front and rear faces of the record disc, of use in investigating the causes of accidents, is braking. Records are made of the time and period of operation, the braking force and form of braking used, whether by foot or hand or by some form of motorized brake. In the indication of r.p.m. a lower or an upper range may be eliminated by providing pin and slot lost motion linkwork between an arm recording the full range of r.p.m. and an indicator arm. In another embodiment, Fig. 15, pencils 94 record speed, mileage and performance on the under side of a disc 89 while a pencil 99 records on the underside of another disc 91. Record sheets. Discs or strips suitable for recording on either or both faces thereof may be prepared by metal spraying or plating, graphite application or by the application of wax. In order to graduate both waxed faces of a disc without the imprints appearing on both sides, discs are prepared separately and joined back to back, preferably the discs are joined by a small land while being prepared, which ensures the coincidence of the graduations when folded for securing back to back. Reading apparatus. To facilitate reading records made on both faces of a disc, the disc is rotatably mounted on a bracket spaced from a plane mirror and part of the disc is embraced by a rotatable cursor formed by two interconnected arms of transparent material offset by the same angle as the front and rear recording pencils, thus facilitating a comparison of the records.