Out of the box, your vx690 terminal comes with a charging cable that looks like the picture below.
The cable plugs into the back of the terminal just below the word 'VeriFone'. We recommend leaving it charging any time the terminal is not in use, however, it is not essential.
WARNING: There is also a port on the side suitable for other USB cables, however, using this port for charging may damage the terminal. Please only use the provided charging cable.