An endless track assembly that mounts to a wheeled vehicle. When a difference between the quantity of the yet-to-be-read data in the FIFO buffer and a value represented by synchronization point information is outside an allowable range, a synchronism evaluation section controls a rate of the data readout from the FIFO buffer in such a manner that the difference falls within the allowable range. An additional feature allows the tip to pivot to various angles with respect to the handle to provide optimum comfort and soldering efficiency. The adapter may include a rotating disc assembly, a wire guide assembly and an electrical connector or wiring harness that may be coiled around the wire guide assembly. Also disclosed is an associated differential pressure sensor. The head comprises a plurality of groups of ink jet elements arranged in M rows and L columns wherein, in particular, the selection and activation of the different columns L are performed, under the control of an external drive circuit, by means of logic circuits inside the head itself.