Electrical frequencies are used by many health care practitioners today, and the number is growing daily. For example, the TENS unit uses specific frequencies for pain control. Low voltage electrical currents to promote the knitting of broken bones was pioneered in Russia years ago, and is not uncommon now in the West. Ultrasound is popular to treat sports injuries, and is used in hospitals and clinics for the general public as well (see Note 1).

One type of generator is produced by reworking an off-the-shelf audio frequency generator (also called a function generator.) These units have a high-current, low-voltage output (approx. 20 volts or less.) A transformer may be employed to bring the voltage up; but this unfortunately filters out the beneficial high and low harmonics that provide the benefits we seek. Another problem with this type of unit is the difficulty of selecting and holding the specific frequency required. The more familiar one becomes with the converted audio generators, the more evident their shortcomings. And the advantages of a unit designed for specific purposes, becomes clear. A specialized instrument does cost more, and there are two reasons why this is so. One reason is the inevitable added cost of advanced engineering. The other is not having the economies of mass production. Remember, most frequency units available today are conversions made from an instrument that is common in the scientific community.They are made and sold by the thousands, thus spreading the cost of research, engineering, manufacturing, and marketing. It might be fair to ask why the "conversion" units cost so much! An off-the-shelf BK 3011 costs about $260. Add some hand grips, foot pads, perhaps a $35 transformer, a new name-plate...and you have a unit that will fetch about $1000 from the right buyer. A good deal...for the seller. An instrument that is designed and engineered specifically for the exacting perameters required by the kind of work we do is 1) more costly to build and 2) sold in far fewer numbers. R&D costs cannot be spread so widely.

What is a fair and reasonable price? Units priced under $1000 are probably reworked audio generators. If so, they are not worthy of consideration. To purchase a quality instrument you will be looking at a price well above $1000, for the reasons outlined above.

Features and capabilities: Buy a unit that has a built-in safety circuit so it cannot produce a high-load charge. It is possible for any electronic device to fail even if it contains the highest quality components. A capability of 60 volts peak-to-peak is recommended. The original Rife/Crane instrument built in the '50s had a 60-volt capacity. Crystal-controlled tuning for accurate frequency selection is a must. Purchase a machine with push-button frequency selection, and Memory. It is very convenient to punch in a frequency and to store a series of frequencies one often uses. Some manufacturers claim a pulsed signal is better, because the body tends to "accommodate" a continuous signal. Microbial researchers question the validity of this claim. In the best units you can select between "pulsed" and "continuous."