A system for monitoring temperature of a subsurface low temperature zone is described. The add-on communication apparatus includes a first communication module to make wireless communication with a terminal, a second communication module to make wireless communication with the in-cable charging control device, and a control module. A multiplyingdividing circuit multiplies the first voltage by the second voltage, and divides the resulting product by the third voltage, so as to generate a fourth voltage. The processor determines the dimensions of the object based on the detected movements and positioning of the user’s hands substantially adjacent to opposing sides of the object.