. The Bell System technical journal . in a single transient photograph of some components in whichthe beam speed may be a thousand times as fast as it is in , beam speeds in excess of 200 kilometers a second are photo-graphed, and a continuous sine wave of 5 megacycles frequency may be 42 BELL SYSTEM TECHNICAL JOURNAL clearly resolved on a single transit. Sweep speeds which permit resolu-tion of much higher frequencies are employed for visual observation,where the transient component being studied can be found by frequentrepetition of the contact operation. As the occurrence of a
. The Bell System technical journal . in a single transient photograph of some components in whichthe beam speed may be a thousand times as fast as it is in , beam speeds in excess of 200 kilometers a second are photo-graphed, and a continuous sine wave of 5 megacycles frequency may be 42 BELL SYSTEM TECHNICAL JOURNAL clearly resolved on a single transit. Sweep speeds which permit resolu-tion of much higher frequencies are employed for visual observation,where the transient component being studied can be found by frequentrepetition of the contact operation. As the occurrence of a particularcomponent varies in time of its position in the entire transient, very highsweep speeds are impractical for photography as a prohibitively largeproportion of exposures would be blanks. A sweep speed of about 15kilometers per second is about as high as is useful except in some specialcases. We may commence the discussion by setting up what appears to bea very simple circuit (Fig. 1), a pair of contacts, one of which is con-. so ^~r VOLTS ^= Fig. 1—Typical relay and contact circuit. nected by a length of wire to a relay winding, which is in turn con-nected to one pole of a 50-volt battery. The mate contact and theother pole of the battery are grounded by very short wires. Theoscillograph is arranged so that the voltage between the contacts andthe current through them can be observed, great care being taken toinsure that the added apparatus does not appreciably change thecircuit characteristics even at very high frequencies. A low powermicroscope may be set up to observe the operating area of the the contacts close, the first thing that happens is the dischargeof the relay structure (a capacity) and of the wire through the wire may be thought of as a radio antenna, more or less open-circuited at the load relay winding terminal, and either grounded oropened at the contacts. The wire forms an oscillatory circuit ofmoderately heavy damping with
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
