Abstract: A distress-signal generator aboard a vehicle includes a transmitter with a self-locking relay for energizing a high-frequency oscillator from a local battery in response to one or more trigger signals from respective detectors, specifically an impact detector and a deformation detector. The impact detector comprises two coacting members, one of them fixed to the vehicle body and the other freely movable with reference thereto, the elastically suspended mobile member being generally spool-shaped and having its waist received in an oblong opening of the plate-shaped fixed member. With the major axis of the oblong extending in the direction of vehicle motion, contact between the two members occurs in response to relatively small transverse and vertical accelerations but only with relatively large longitudinal acceleration; relative torsion is detected by a horizontal pin on the mobile member bracketed by two stops on the fixed member normally spaced therefrom.