Throughout The Troubles , the Provisional IRA made extensive use of IEDs in their 1969 – 97 campaign . They used barrack buster mortars and remote controlled IEDs . Members of the IRA developed and counter-developed devices and tactics . IRA bombs became highly sophisticated , featuring anti-handling devices such as a mercury tilt switch or microswitches . These devices would detonate the bomb if it was moved in any way . Typically , the safety-arming device used was a clockwork Memopark timer , which armed the bomb up to 60 minutes after it was placed by completing an electrical circuit supplying power to the anti-handling device . Depending on the particular design ( e.g. , boobytrapped briefcase or car bomb ) an independent electrical circuit supplied power to a conventional timer set for the intended time delay , e.g. 40 minutes . However , some electronic delays developed by IRA technicians could be set to accurately detonate a bomb weeks after it was hidden , which is what happened in the Brighton hotel bomb attack of 1984 . Initially , bombs were detonated either by timer or by simple command wire . Later , bombs could be detonated by radio control . Initially , simple servos from radio-controlled aircraft were used to close the electrical circuit and supply power to the detonator . After the British developed jammers , IRA technicians introduced devices that required a sequence of pulsed radio codes to arm and detonate them . These were harder to jam
Brighton hotel bomb attack
Brighton hotel bombing
Improvised explosive device