Abstract: A microcontroller based multiple access unit for use in interconnecting a plurality of computers with a token ring data network. The microcontroller monitors a phantom voltage applied by a computer to determine whether the computer should be inserted into, or withdrawn from, the network. The microcontroller also monitors a manual activation device to determine whether any computer that is not providing a phantom voltage is still interconnected to the network. In such a case, the microprocessor withdraws the computer from the network. A coil-pair is directly interconnected to a plurality of microprocessor gates. The microcontroller activates the coil-pair in one manner to cause the computer to be brought into the network and reverses the plurality of the coil-pair so as to withdraw the computer from the network. The controller further includes a circuit to inhibit operation of the microcontroller when the supply voltage is unstable.