A system for remotely authenticating credit card transactions of a consumer comprises at least one subsystem that alerts the consumer via a communication device of the consumer when a credit card transaction that meets certain criteria is being attempted on the consumer’s credit card account. Switching means are provided for switching the impedance of the amplifier between two reflecting states such that the reflected and amplified signal is phase modulated. The diode prevents current flow from the conductive brush to the direct-current power source, and thus the paper dust collected by the conductive brush will not return to the photosensitive drum.