A switching function is performed in response to a predetermined rate-of-change of an output signal, thereby providing rate-of-change switching. Rate-of-change switches (63 and 154) each include a user-controlled transducer (38A, 38B, or 39), a differentiator (40A, 40B, 112, or 156), and a discriminator (42, 114, 134, 160, or 162). The rate-of-change switches (63 and 154) perform at least one switching function when an output from the differentiator (40A, 40B, 112, or 156) or a second differentiator (158) exceeds an allowable magnitude. The rate-of-change switches (63 and 154) may be used to control a timed-opportunity switch (26 or 172), a conveyance, such as a wheelchair (12), and such functions as extending and retracting leg supports, and/or an environmental control unit (14 or 174). The rate-of-change switches (63 or 154) may be attached to a body member (18, 64, or 67) and be actuated by body-member gestures.