GB919765A - Improvements in or relating to warning devices - Google Patents

Abstract

919,765. Transistor circuits. NORMALAIR Ltd. Jan. 11, 1961 [Feb. 2, 1960], No. 3575/60. Class 40 (6). [Also in Groups VI, XXI and XXXVIII] An audible warning device automatically gives a signal if no motion of the device is detected during a predetermined period. The switch contacts S1, which are normally held open by the insertion of a key (not shown) into the container (not shown) housing the device, are closed by removal of the key. The movement sensing means 2 maintains a circuit between its terminals as long as it is in motion, but open-circuits them when it is at rest. In the latter condition the capacitor C1 is charged through resistor R1 and provided the means 2 remains at rest for about 40 seconds the potential at the base of transistor 3 becomes such that the transistor conducts and operates relay 4, which locks up over contacts S2 and applies operating potentials via S3 to multivibrator 7 which intermittently energizes the electric horn 5. The horn continues sounding until relay 4 is released by re-insertion of the key. The horn may be sounded, if desired, by manual closure of switch S4, independently of the condition of means 2. In a modification (Fig. 1, not shown), contacts S3 complete a local circuit for continuous sounding of horn 5. The device may be carried by a fireman or rescue worker and will signal the fact that he has not moved for a predetermined time.