There are many advantages of Longwave Diathermy, which is also called as CET technique. There are three manufacturer SKanlab , Indiba and Biotech .
It radiates much less than Shortwave Diathermy as Frequency of operation is less than 1MHZ and Power is below 75watts, where as SWD has frequency of 27.12Mhz and power of 250watts and above.
There are studies, which shows, it gives better result than SWD and Ultrasound.