A pressure-sensitive switch (16; 116; 216) comprising: a base member (32; 132; 232) having a mounting surface (36; 136; 236) formed of electrically-insulating material; and a flexible diaphragm (34; 134; 234) having a peripheral portion fixedly secured in a fluid-tight manner to the mounting surface (36; 136; 236) such that a gas-tight chamber is formed between the flexible diaphragm (34; 134; 234) and the mounting surface (36; 136; 236) of the base member (32; 132; 232), the gas-tight chamber having a predetermined pressure that is adjustable, the switch (16; 116; 216) including first and second electrodes (38, 40; 238, 240) mounted on the base member (32; 132; 232), each of the electrodes (38, 40; 238, 240) having an exposed, electrically-conductive contact surface disposed adjacent the mounting surface (36; 136; 236) of the base member (32; 132; 232), the flexible diaphragm (34; 134; 234) having a central portion (64, 66, 68, 70) overlying the contact surfaces of the first and second electrodes (38, 40; 238, 240), at least the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) being formed of electrically-conductive material, being exposed to the pressure surrounding the switch (16; 116; 216), and being formed with plural corrugations (66, 68, 70), each having a trough, such that when the switch (16; 116; 216) is exposed to atmospheric pressure, the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) is spaced from the contact surfaces of the electrodes (38, 40; 238, 240), but when the switch (16; 116; 216) is exposed to a pressure substantially in excess of atmospheric pressure, at least one trough of one of the plural corrugations (66, 68, 70) of the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) is forced into contact at the predetermined pressure with both the contact surfaces, thereby electrically connecting the first and second electrodes (38, 40; 238, 240) to each other, and the switch being characterized in that: when the switch is exposed to the pressure substantially in excess of atmospheric pressure the at least one trough of one of the plural corrugations (66, 68, 70) is forced into contact at the predetermined pressure with the mounting surface (36; 136; 236) of the base member (32; 132; 232). a base member (32; 132; 232) having a mounting surface (36; 136; 236) formed of electrically-insulating material; and a flexible diaphragm (34; 134; 234) having a peripheral portion fixedly secured in a fluid-tight manner to the mounting surface (36; 136; 236) such that a gas-tight chamber is formed between the flexible diaphragm (34; 134; 234) and the mounting surface (36; 136; 236) of the base member (32; 132; 232), the gas-tight chamber having a predetermined pressure that is adjustable, the switch (16; 116; 216) including first and second electrodes (38, 40; 238, 240) mounted on the base member (32; 132; 232), each of the electrodes (38, 40; 238, 240) having an exposed, electrically-conductive contact surface disposed adjacent the mounting surface (36; 136; 236) of the base member (32; 132; 232), the flexible diaphragm (34; 134; 234) having a central portion (64, 66, 68, 70) overlying the contact surfaces of the first and second electrodes (38, 40; 238, 240), at least the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) being formed of electrically-conductive material, being exposed to the pressure surrounding the switch (16; 116; 216), and being formed with plural corrugations (66, 68, 70), each having a trough, such that when the switch (16; 116; 216) is exposed to atmospheric pressure, the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) is spaced from the contact surfaces of the electrodes (38, 40; 238, 240), but when the switch (16; 116; 216) is exposed to a pressure substantially in excess of atmospheric pressure, at least one trough of one of the plural corrugations (66, 68, 70) of the central portion (64, 66, 68, 70) of the diaphragm (34; 134; 234) is forced into contact at the predetermined pressure with both the contact surfaces, thereby electrically connecting the first and second electrodes (38, 40; 238, 240) to each other, and the switch being characterized in that: when the switch is exposed to the pressure substantially in excess of atmospheric pressure the at least one trough of one of the plural corrugations (66, 68, 70) is forced into contact at the predetermined pressure with the mounting surface (36; 136; 236) of the base member (32; 132; 232).