WASHINGTON— Two brothers in Paterson, N.J., have patented an electrical "cranial stimulator," which, they contend, can relieve physical pain, as well as depression, anxiety, insomnia and even jet lag.

Getting a patent does not mean that an invention actually works well, but the inventors, Saul and Bernard Liss, say they have human tests to support their claims, and some medical doctors say they use it on their patients.

Because the device is similar to one that was approved in the 1970's by Federal regulators for treating certain symptoms, it is already being sold. The price is about $900.

The Liss invention is similar to a well-known product to relieve muscle pain called TENS, for transcutaneous electrical nerve stimulator. A TENS device uses two or more electrical contacts to send an electrical current of 80 milliamps through the skin. The current is believed to interfere with the passage of pain signals in the nervous system.

The new device also uses two or more contacts, at least one of which is placed on the side of the skull, and transmits a current that fluctuates at very high frequencies.

Saul Liss said the device appeared to change the levels of certain chemicals in the brain, called neurotransmitters, that affect both physical well-being and mood.

Physicians in New York have published results of a study of migraine headaches that indicated that the device provided double the pain relief of a placebo device.

In addition, Dr. C. Norman Shealy, a neurosurgeon who worked with the original TENS technology, said he had been using the Liss device for years at his Shealy Institute for Comprehensive Pain in Springfield, Mo.

Saul and Bernard Liss received patent 5,109,847.