Method for transmitting signals between a microprocessor and an interface circuit

A control module (11) in an airbag system (10) supplies electrical energy to and communicates with remote modules (20A-20N) through a two-wire connection. The supplied electrical energy is partially used to operate the remote modules (20A-20N) and partially stored within the remote modules (20A-20N) for deploying squibs (22A-22N). The control module (11) sends command signals to the remote modules (20A-20N) via voltage excursions between a high and an intermediate voltage levels. The remote modules (20A-20N) send signals to the control module (11) via current excursions. When an accident situation is detected, the voltage across the two-wire connection is lowered to a low voltage level, thereby interrupting a normal operation of the airbag system (10). The control module (11) then sends out firing signals via voltage excursion between the intermediate and low voltage levels. The remote modules (20A-20N) decode the firing signals and deploy the squibs (22A-22N) to inflate airbags.