EYE MISSES NOTHING

Grey River Argus, 8 November 1939, Page 2

EYE MISSES NOTHING

Westminster Abbey’s treasures, are now protected every night from terrorists by “invisible ray” alarms, 'it is announced. Beams of invisible flight, stretch before them, and the I intruder who, knowingly breaks one ’himself gives the alarm. | Not only the Abbey. Many, big stores, warehouses, art galleries and private homes are nightly criss-cross-ed by these “black searchlights.” Directly one is interrupted an electric .relay sounds the alarm. , In one or I two stores it operates a direct, lino to I the nearest police station, switches on all lights, and can even trap its : prey behind steel shutters. I The "photo-electric” cell, as the 'gadget is called, is one of science’s most utilitarian products and is saving mankind from a vast amount of I monotonous, brain-breaking labour. ‘There isn’t much to it. Just a sensitive metal plate which produces a tiny electric current when light falls on it, the amount of current varying 'with the light. When it was first discovered, they thought it might be used to turn sunlight into •electric energy, but. since then industry has taken it up in a big way and to-day it comes into our lives a dozen times a day. j Counting is the cell’s star turn. It never makes a mistake. When the builders of the Mersey and Holland Tunnels were asked to fit a vehicle-mounting gadget, they chose I the cell at once. Sunk in the roadway of each traffic-track, they fitted [a number of cells. From the ceil|ing little beams of light shone down. (Now every vehicle which passes breaks a beam; the cells react, and ■an electric adding machine does the rest. | A minute cell even checks up on the purity of air in the great tunnel. From one of the outlets stale {air is drawn through a beam of {light which is so focussed that normally it just misses the sensitive cell. But if fumes thicken the air the light tends Co diffuse (like a headlight in fog) and to shine on rhe cell. A bell warns the ventilating engineers. But the cell has a more vital job I than that of saving headaches. It {protects lives from lire. Nowadays, {every big liner and many a freighter I s protected by automatic fire-detect-ors. The cell again. From every hold, public room and enclosed space ( air is drawn through pipes and passed before a battery of cells on which lights shine. The least wisp of smoke—drawn from a lire smouldering deep in the far-off hold—clouds the light, operates the cell, and sounds the alarm.

I From tire to fish. In a big spratpacking works a cheap, infallible gadget was needed to sort the stream oi fish into three sizes. Previous i men had done the job, but found it so monotonous and tiring that. 15 min--utes was the maximum shift. The cell saved that. i An endless belt was installed which carried the fish, tail upward, past I two beams of light shining on to two | cells, one above the other. The smallest fish did not cut through j ,'either beam and passed on. The I , medium fish cut the first beam, and | were automatically dropped into the ( appropriate bins. The biggest fish cut through both beams, and were released accordingly. Factory owners have found scores of similar uses for the cell, which will count and grade objects of any kind. That it displaces human labour is possible, but only labour of a kind which is an insult to any human mind. And again, in the factory it saves lives. It can be fix-

ed that a big press, say, or a saw or moving arm is instantly checked if the attendant worker’s hand comes within the danger area and breaks a beam of light. Safety on the railways too. On some systems a cell is used to switch

on a train’s brakes automatically if it should pass a clanger signal. A tiny vane attached to the signal breaks a light beam carried by the passing locomotive. Safety for pedestrians . . . In London recently a cell apparatus, vhich halted the traffic whenever a pedestrian approached the • curb to cross, was installed. As he moved road wards, the walker passed through a beim of “invisible light." I The cell passed on the message to 'the traffic lights. They were in turn informed of the state of trafiic by other cells. Their metal brains clicked. Directly traffic conditions were suitable, a warning light flashed. The walker or walkers crossed. Safety for crockery . . . Heavily laden waiters approaching swing doors do nol have to push, stand in no danger of being pushed. As they pproach the door, they break a ray — and the door swings open automatcally for them. The photo-electric cell isn’t paricular about the sort of light it recivto. Plain electric light—like the cam across race tracks used to time ic/rses or runners to a hundredth of a second. Daylight—many London street lamps are turned on automatically when the daylight on a cell falls below a certain level. Or “invisible light” at extreme ends the spectrum which .you and I and burglars can’t detect.