Switch Interface Relay Switch Interface Relay “Basic Environmental Control Devices for Persons With Severe Multiple Handicapping Conditions,” GiangrecoMichael F, EdS; National Clearinghouse of Rehabilitation Training Materials, 115 Old USDA Building, Oklahoma State University, Stillwater, Oklahoma 74078, 405–624–7650. The Switch Interface Relay (SIR) is one of several devices that can be constructed from the above manual. It consists of a 7.5-in. by 4.5-in. by 2.25-in. rigid plastic case, 110-v power outlet, 6-ft power cord, and internal relay. The SIR allows electrical devices to be operated by persons with severe handicapping conditions. Approximate cost of materials required to assemble the SIR: $40.