An ion implanter system including an ion source for use in creating a stream or beam of ions. The invention is a unique combination of an adjustable gain, bidirectional amplifier, a GPS receiver, a processor, and one or more removable, non-volatile, updatable memory devices. The IUs perform control operations so that part of signals to be applied to each of the MODEMs isare applied only when an activation signal for the MODEM is enabled. The sheet feeder includes a roller for feeding the sheet from the tray.