Abstract: A three mask method is provided for making a field effect transistor which includes the use of a first mask for defining first and second spaced apart diffusion regions, each having first and second ends, a second mask for defining a contact region at the first end of the first and second diffusion regions and for defining a protected region at the gate region and source and drain electrodes of the transistor, the protected region extending between the second ends of the first and second diffusion regions, and a third mask for forming a gate electrode within the protected region and contact electrodes in the contact region. The source and drain electrodes are formed between the gate electrode and the first and second diffusion regions by ion implantation techniques.

Abstract: A control system having a plurality of control channels each having its own source of system hydraeric fluid under pressure and each having a control valve and a monitor valve. A position indicating pressure signal is generated by each of the valves and is compared to detect discrepancies therebetween, and in the event of such a discrepancy, to generate a failure indicating signal. The failure indicating signal is subsequently transmitted to appropriate control apparatus which will effect proper switching to eliminate any part of the failed system from control or future possible control of the apparatus to which the system is connected.