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I could not fathom the method used, but the commander of our craft clamped what looked like a pair of headphones against his body and plugged the end of a wire leading from them into his instrument board. From time to time various colored lights glowed on the board before him. After a time he uncoupled his device from the board, and one of the long rods shot out from our ship to the other.

The ordeal seemed to last for centuries. Actually it could be measured only in minutes. But it seemed millennia before the headphones said, staccato fashion: "You are on course and will reach speed in fourteen seconds. I will count for you." "Relays for rocket release," panted Joe. "Throw 'em over!" Three hands moved to obey. Joe could release the drive rockets on all seven ships at will.

The result is that these oscillations of different frequencies interfere and reinforce each other when beats are produced, the period of which is slow enough to be heard in the headphones, hence the incoming signals can be heard only when waves from the sending station are being received. The Autodyne or Self-Heterodyne Long-Wave Receiving Set.

Then Sally's voice sounded in the headphones Joe wore. He was relieved that Mike wasn't acting as communications officer at the moment to overhear. But Mike was zestfully spinning like a pin-wheel in the middle of the air of the control cabin. He was showing the others that even in the intramural pastimes a spaceship crew will indulge in, a midget was better than a full-sized man.

A short wave receiving set is one that will receive a range of wave lengths of from 150 to 600 meters while the distance over which the waves can be received as well as the intensity of the sounds reproduced by the headphones depends on: whether it is a regenerative set and whether it is provided with amplifying tubes.

Metcalf spoke into his wireless telephone transmitter was caught and swelled in volume by the Telemegafones below and persons blocks away could hear the message plainly. Two kinds of these loud speakers are made and these are: a small loud speaker for the use of operators so that headphones need not be worn, and a large loud speaker for auditorium and out-door audiences.

If you want to add an amplifier tube then connect it to the posts instead of the headphones as described in the foregoing set. All receiving sets that receive over a range of wave lengths of from 150 meters to 3,000 meters are called intermediate wave sets and all sets that receive wave lengths over a range of anything more than 3,000 meters are called long wave sets.

For this set you require: one variocoupler; two variometers; one .001 microfarad variable condenser; one .0005 microfarad variable condenser; one 2 megohm grid leak resistance; one vacuum tube detector; one 6 volt A battery; one 200 ohm potentiometer; one 22-1/2 volt B battery; one .001 microfarad fixed condenser, and one pair of 2,000 ohm headphones.

Check it." The Chief muttered, "Something whacky here ... come round, you! Okay, Joe." Joe had no time for reflection. He was in charge of the clumsiest operation ever designed for an exact result. The squadron went wallowing toward the sky. The noise was horrible. A tinny voice in his headphones: "You are at 65,000 feet. Your rate-of-climb curve is flattening.

The amplifier tube is a variable relay in that the feeble currents set up by the incoming waves constantly and proportionately vary a large current that flows through the headphones. This then is the principle on which the amplifying tube works. The Operation of a Simple Vacuum Tube Receiving Set.