A vehicle's restraint system for passengers such as airbags, belt tighteners or similar devices to protect the passengers in case of a crash against injury including an electronic sensor circuit for the release of the restraint system, only upon the occurrence of predetermined conditions. An energy supply is provided for supply of the electronic sensor circuit with a proper and set voltage value to be monitored at least from time to time and compared with a reference voltage wherein at least an emergency voltage supply is to be held in a steady state such as at the set voltage value to provide power to electrically ignite a pyrotechnic or propellant charge if triggered by said electronic sensor circuit, in the case that one or more of said predetermined conditions evaluated in said electronic sensor circuit by comparing it with chosen threshold values are fulfilled, indicating that a crash event is detected by an acceleration responsive signal generator in said electronic sensor circuit. An electric cell is provided in communication with said energy supply for recharging at least the emergency source thereof to said steady state. An optical connection is provided for optical connection to said opto-electric cell including a light emitting element connected to a light receiving element via a light guide so arranged as to achieve said recharging of one of the sources being accumulateable when a light source emits light.