1. An apparatus, comprising:a plurality of sensors, wherein each of the sensors is configured to generate a frequency carrier; and
a plurality of nodes, wherein each node in the plurality of nodes is connected to a corresponding one of the sensors, wherein each node is configured to:
amplitude modulate the frequency carrier from a corresponding one of the sensors to uniquely identify that sensor; and
transmit the amplitude modulated frequency carrier to a receiver, wherein each node in the plurality of nodes comprises:
a first path including an amplitude modulator; and
a second path including a code generator, wherein the amplitude modulator is configured to amplitude modulate the frequency carrier by a code sequence generated by the code generator.