Here's an excerpt from a great piece by Michael Yon that's running over at sister site, Line of Departure, detailing the Afghan insurgents latest move to counter Western anti-IED tech; the "snapper" bomb.
As Yon explains it, the U.S. and its allies have become very adept at defeating the radio controlled bombs that were hitting coalition troops in Iraq and Afghanistan several years ago; and while simple pressure plate mines can't be jammed they can be triggered by anyone, not just the intended target. This can create civilian casualties and waste the bomb. Enter the low-tech, remote controlled snapper:
The snapper uses a tire for a diaphragm in which nails are used for contacts. When a vehicle rolls over a snapper, the circuit closes. To avoid CIVCAS, the enemy waits in hiding with a battery. One of the electrodes is connected. Traffic is allowed to roll over the snapper but there is no explosion. When the target approaches, the enemy attaches the other connection and now the snapper is ARMED.
When the circuit closes this time, juice flows to the bomb, which must be very substantial to defeat our armor, but if the target is lesser-equipped Coalition forces or perhaps unarmored Afghans, it can be small.