A display driving circuit includes a first interface unit, a signal discriminating circuit, a signal distributing circuit, a driver logic circuit and a synchronization processing unit. The housing has a first housing part of a first, resilient plastic material and includes a resilient latch portion for latching engagement with the complementary connecting device. The facing portions of the barrel cage and trigger housing is provided with a mating configuration which enables the gun to be easily assembled for use and easily disassembled for storage in a toolbox.