Another use for the Diathermy Machine

“So, what exactly is diathermy?” 

As I expected, I got a five minute mini-lecture, most of which I didn’t understand, and all of which I’ve forgotten. Yet, I wasn’t told exactly what it was.

I should explain: diathermy or electro-coagulation uses a high-frequency current to heat, and thus coagulate, small blood vessels. It spreads from the ‘active’ pole, usually whatever is being held in tweezers, and returns to the ‘collecting plate’. It’s been around from before the second World War.

“Just what sort of a current is it?” Again, another mini-lecture.

“So, why don’t we just use ordinary mains electricity? It’s an alternating current, after all, like diathermy is.”

Now, that stumped them for a while. Actually, that is quite simple; ordinary electricity at 50 Hz (cycles per second) can interfere with the heart’s pacemakers, and cause sudden death — one way that people can be electrocuted.

“It’s a radio frequency current.”

“That’s what I said.”

“Without using the words radio frequency, or explaining why it must be.”

“A radio frequency alternating current won’t interfere with the pacemakers. That’s why it’s safe — provided all the correct precautions are observed.”

They looked suitably smug. Sir clearly hadn’t followed the lectures.

“So, can you imagine any other use for diathermy machines?” Now, this was a bit naughty of me, but Sir does have to be at least one step ahead of the young chaps, to keep them in their place.

They couldn’t. I wasn’t surprised.

“This is a strange story. In the early days of the Blitz, the Germans used to fly along a directional radio beam; and when they crossed a second directional bombs, they knew they were at the target. The British initially thought that a directional radio beam was impossible, but sent up a plane to check it out. It was true. So there was the problem of jamming those radio beams. A senior officer went round the surgical suppliers, gathering up diathermy machines. These were then sent to village policemen on the south coast, and when directional beams were found, the policemen got instructions as to how to change the settings on the machines. It actually worked, the directional beams were blocked.”