A system for signal transmission along a drill string is disclosed. A first drill pipe section and a second drill pipe section each comprise an inner pipe. A first repeater sub is coupled to the first drill pipe section and the second drill pipe section at a first position along the drill string. The first repeater sub comprises a first toroid corresponding to the first drill pipe section and a second toroid corresponding to the second drill pipe section. A signal transmitted through the first drill pipe section, an inner mandrel of the repeater sub and the inner pipe of the first drill pipe section is received by the first toroid. The first repeater sub processes the signal received by the first toroid to generate a processed signal and transmits the processed signal to the second drill pipe through the second toroid.