An electrical circuitry fitted to be connected or to be an integral part of a bone fixation device having at least one linear actuator coupled between two rings, including: at least one linear actuator connector, mechanically and/or electrically connectable to said at least one linear actuator； a control circuitry, wherein said control circuitry measures a value related to the movement of said at least one linear actuator and/or to the distance or change in distance between said two rings, by receiving signals from said linear actuator connector； and a memory, wherein said memory stores said value.
