Abstract: An electrode assembly is mounted in a helmet like headset for use in making multiple electrode contact with the scalp. Each electrode assembly includes an electrode that floats in a cylinder mounted in a pressure responsive drive, which, when under pressure carries the electrode toward the scalp of a patient wearing the headset. Mounted in the cylinder above the electrode and biased away from the electrode is an LSI chip carrying an operation amplifier and a power supply for the amplifier. When the electrode makes contact with the scalp the cylinder continues to drive forward. Back pressure from contact with the scalp overcomes the bias and completes a circuit to turn on the amplifier. The amplifier is connected via wire or a wireless signal transmit system to a computer into which amplified signals are fed.