Koninklijke Philips Electronics N.V. (NYSE:PHG) is suing Zoll Medical Corp. (NSDQ:ZOLL), accusing the Chelmsford, Mass.-based firm of violating a string of automated external defibrillator patents with its AED Plus and AED Pro devices.

The lawsuit, filed in the U.S. District Court for Massachusetts, alleges that Zoll willfully violated the 15 patents despite Philips notifying the company of the alleged infringements in November 2008, according to court documents.

The lawsuit seeks a jury trial, an injunction barring further infringement, damages and interest on the alleged infringement, extra damages for the allegedly willful violation of the patents and legal fees.

External defibrillators are big business for both companies. Last fall, each won lucrative contracts from the U.S government to supply the devices, which are used to shock the heart back to beating after a heart attack. Zoll won a $29.8 million contract from the Defense Supply Center in Philadelphia to provide its CCT defibrillators to the U.S. Army, Navy, Air Force, Marine Corps and federal agencies; Andover, Mass.-based Philips Healthcare won a $26.6 million deal from the Dept. of Defense’s Philadelphia supply center to provide its HeartStart MRx defibrillators to the same cast of military and federal agencies.