An apparatus is provided which includes a peripheral device and a bracket. The method includes: providing a predetermined voltage to the differential output for obtaining an accurate current passing through the panel resistor during a calibration procedure and, providing a driving current to the differential output according to the accurate current during a normal operation procedure. The power headroom report comprises a first type power headroom and a second type power headroom. In response to an indication that the name of the calling party is unavailable, the method accesses the databases and searches for the matching telephone number and corresponding city and state names.