Looking at World War II aviation, some sensitive items were fitted with small explosive charges to prevent capture, typically radio or radar sets; capturing such devices was enormously helpful in the field of electronic warfare. Identification Friend or Foe (IFF) transponders allowed radar operators to identify friendly aircraft, and Allied sets were fitted with detonators; from the P-51 pilot's flight manual:

"The IFF set has a detonator to destroy vital parts of the equipment if you have to abandon the airplane over unfriendly territory. The detonator is set off by pressing two push button switches which are in a box on the right side of the cockpit. Both buttons must be pressed simultaneously."

You can see a similar set-up in a Spitfire cockpit [on this page] (http://spitfiresite.com/2010/07/anatomy-of-spitfire-cockpit.html/03cn7804), with the warning plate marked "DANGER" over the two buttons.

The charges were small, just enough to wreck vital components; in 388th Anthology: Tales of the 388th Bombardment Group, a B-17 radio operator writes "As per standard procedure, as soon as the plane became airborne on take-off, I plugged in the Identification Freind or Foe (IFF) unit at which time the self-destruct charge went off. It was like a shotgun blast. The sides of the unit were bulged out, with a good bit of smoke and some small flames."; the aircraft continued the mission.

Another example could be found on the REBECCA-EUREKA direction finding/homing beacon system. [This film from the Imperial War Museum] (http://film.iwmcollections.org.uk/record/index/3706) includes:

"10:21:38 A roller caption explains the importance of preventing any REBECCA and EUREKA equipment from falling into enemy hands in order to avoid the danger of effective German electronic warfare counter-measures resulting from the capture of any intact examples. The method of actuating the push-button demolition charge on the REBECCA;s voltage control equipment and priming the EUREKA's transmitter/receiver unit for destruction are demonstrated for the camera. A complete EUREKA set is seen being blown apart with its small demolition charge. The camera examines the burnt and twisted fragments of metal produced by the explosion. "