An envelope filling machine for introducing sheets into envelopes includes a sliding surface, for transferring the sheets to an envelope filling station by means of pushing lugs, operated along the sliding surface. The switch instructing unit monitors the state of the REC device, and based on a result of the monitoring, determines switching from the REC device to an extension REC device. The modular construction includes a housing having a plurality of bores formed therein into which is press fit long pins and short pins for electrical communication with an external power source and an internal customer telephone circuit, respectively. The cutting elements can be evenly distributed about the circumference of the tool at the same radial distance such that the tips of the cutting teeth and also the seats define a common cylindrical envelope surface the axis of which coincides with the axis of the tool body.