1931-02-05 — Page 2

HONG KONG DAILY PRESS, THURSDAY, FEBRUARY 5, 1931.

MUSIC FROM MANY COUNTRIES by wireless with

TELEFUNKEN 40

Long range All-Electric receiver with station selectoe for use with. batteries or lighting main.

with TELEFUNKEN ́

LOUDSPEAKER

ARCOPHON

TADIO

For Demonstration and further particulars apply to -- SIEMENS CHINA CO.

TELE FUN KEN

Office-Pedder Building, 4th Floor.

Showroom-27, Nathan Road,.

Kowloon.

Canton Office-Shameen. Swatow -Gebr. Roese.

35

TELEFUNKEN

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DISTRIBUTORS.

FEATURES

SIMPLE FORMULE YOU SHOULD KNOW.

THE RELATION BETWEEN VOLTAGE CURRENT AND

RESISTANCE.

ETHER DISTURBED 186,000 MILES AWAY IN ONE SECOND.

To a novice in radio, the very | word formula is apt to intimidate. But there are some formula that must be grasped before one can graduate in the bow and why of Radio.

by frequency; that is, frequency equals 300,000 kilometres divided by 300 metres, which equals 1,000 kilo cycles. It is often useful to, inter- pret wavelengths as frequency, for the stations of Europe are separ- The easiest radio. formula tonted (or are supposed to be) by understand relates to wireless kilocycles. Looking up an offcial sce Aberdeen on 301 waves, their speed, their frequency list we can and their wavelength, This for- metres, with a corresponding fro mula atates that the wavelength of quency of ves kilocycles. a station is equal to the speed of the waves, divided by the number of waves emitted per second.

Wavelength and Frequency, All wireless waves travel at the same speed, the speed of light, 186,000 miles per second. In terms of the existing theory of the ether, through which medium wireless waves are said to be transmitted, we can say that when a wireless ware vibrates at a given point, the ether is disturbed one second later at n point 186,000 miles away. ̧

Whatever way one visualises the velocity of wireless waves, the fact remains that all stations, send out waves of the same velocity: 180,000 miles per second, or 300,000 kilo- metres per second. The frequency with which wireless waves are sent out depends entirely upon the tan- ing circuit of the transmitter. We can look upon frequency as the number of waves passing a given point in a second.

Since all waves travel at the same speed, the greater the number that pass a given point in a second, the shorter must be the wavelength of esch. This fact is easy to under- stand and is expressed in the for- mula: wavelength equals speed divided by frequency. Knowing any two of these, we can therefore determine the third.

Ohm's Law.

Now let us deal with the most used formula in radio, Ohm's Law. This Law states that "the current is directly proportional to the E.M.F., and inversely proportional to the resistance." Before we can interpret the law let us understand ita constituents.

Current, E.M.F. and resistance Current is the need explaining. measure of the rate of flow of elee tions, the movement of which સ electric current. constitutes

of current is the The unit ampere, and we say an ampere is the rate of flow of one coulomb per second. We are not often con carved with the actual amount of electricity, but we always want to know the rate of flow. So forget coulombs, and remember that one ampere will flow through a closed circuit when a pressure of a volt is impressed upon it, and when its resistance is 1 ohm. the measure of the rate of flow of electricity. The unit of current is the ampere.

Current is

as electro, Voltage, known als motive force, electric pressure and potential difference, is the term used to denote the force that tends to cause electricity to flow. Cur rent flow is coulomba per second. Suppose we have a wavelength of The analogy in celar for current. 300 metres. As we already now It also holds good for voltage. As the velocity is 300,000 kilometres water pressure is measured in per second, we can easily work outpounds, per square inch, electric the frequency. Thus 500 metres pressure is measured in volts. The equals 300,000 kilometres divided unit of electric pressure is the volt,

FILM SENT BY TELEVISION.

CLEAR IMAGES ON A 24-FT.

SCREEN.

Consideration is being given by the British Broadcasting Corpora tion to a new system of television, invented and developed by His Mastor's Voice Gramophone Com- pany.

After many months of work in their research laboratories at Hayes (Middlesex) & number of technical exports of the Gramop- hone Company have developed the new system to, such an extent that clear, moving images can be thrown on a screen 24ft by 20ft, or evou larger.

The image is so clear that wire getting shows up distinctly at the receiving end with each, individual mosh defined.

It is possible that the invention may be given a triad by the Broad- casting Corporation just as the. Baird system has been tried out for the past few months,

Oricket and Racing.

At a lemonstration of the new system o cinematograph film was telegraphed between the transmit- ter and the receiver, and moving pictures of circket match incidente and racing were shown upon the stroen.

An official of the company said yesterday: "Moving pictures were telegraphed at the rate of 1214 second across a distance of from 20 to 30 feet.

"The distance was simply a matter of convenience. If it can - bo dano across 20 foot it can be

Brichy, the now systein brEINE the picture up into five sections, cach of which is dealt with by a separate photo electric cell. The five sections are them thrown upon the receiver screen together again

4 one picture.",

which is the electro-motive forre needed to force the current of one ampare through a tesistance of one' ohm.

That brings us back to Ohm's Law, for there is no difficulty in visualising resistance, which in elec tricity is clearly analogous to frie Resistance is tion in mechanics. the property of matter opposing the flow of electrons, which flow tends to take place when a differ ence of potential or voltage is intro. duced.

Now we can understand the

I = E/R meaning of

or in other words current (1) in am. peres, equals voltage (E) in volts, This is the practical expression of divided by resistance (R) in ohms. Ohm's Law. The equation can be expressed in three different ways so that an unknown. quantity can be worked out if the other two quinti- tics are known. (1) Current equals voltage, divided by resistance. (2) Resistance equa's voltage divided by current. (3) Voltage drop equals current multiplied by resistance.

Let us apply these three equa tions to three simple problems. A closed circuit with a potential dif ference of a volts and a total resist- ance of 2 ohms. What current is flowing 7 From equation (1) we get

1:

0/2 = 9.

A closed circuit with a potential difference of 12 volts and a current of 3 amperes flowing. What is the resistance? From equation (2) we got

R = 10/3.4.

Take a current flowing at 1 am- pere and a resistance is G ohms. What is the voltage drop across the

got resistance? From equation (3) we

E = 1 X

So the voltage drop across the resistanco of is 6 volts.

HAVE YOU HEARD THESE?

Here are lists of long-wave and short-wave stations which should be picked up by anyone in Hong Kong who has a mode rately good set suitable for re- ceiving such signals. Success in picking up these stations also depends very largely upon fav. ourable atmospheric conditions.

Bonders are invited to adit to this list should they succeed in picking up. ang atation not” in- cluded in either of these lists.

07.65 Debints (Germany)

LONG-WAVE STATIONS.

Call Kilo-

Wave length

(Metres) Station

200, Manila 277 Shanghai 980 Tientsin 310 Shangbai

220 Peping

880 846

840

830

Sign cyclo K2I.P. 1,sa K.S.M.S. 1,085 C.R.C.. 1,070 K.R.C. 907- C.O.P.K.. 945 345 Tokyo J.O.A.K. F70 383 Hiroshima J.O.F.K 35% Hong Kong Z.B. W. 367 Bombay V.U.B. 361 Supporo J.O.LE 366, Keijo 370 Nagoya 370.4 Calcutta 380 Kumamoto 390 Sendzi 395 Dairen 398 Rangoon .400 Osaka

410 Canton

Kito

Стек

J.O.D.E. 820

900.0

סדר

J.0.0.K. 810 V.U.C 3.0.G.K. 790 3.0.H.K. J.D.A.K 760 V.U.R. ·754 J.O.B.K. 760 "C:M.B. 789 K ZR.M. 796

Time (Hono Kono)

413 Manila

SHORT WAVE STATIONS,

STATION

CALL SIGH

Perth

0.19, Khabarovsk (Russia) 56. NALLON 60. Moscow

Bemo 43,8

A.F.K B.A.7.

4,484 Mon, Wed. & Fri., 6 p.. & 3 mm,

4,990 6-10 fum,

A.G.J. RF.N..

5,291 Not regular

IM.A

41.8

Bingapore

28,8

Kootwijk (Holland)

F.C.L.

H.S.4.P.J.

82.57 Bydney, ⠀

31.55 81.48

2.B.L. 8.1.0

42

37 Bangkor (Biam)

Halloumno

Schenectady

BA... V.B.1.A.D.

6,000 Tue, Thurs, Est; 8pm,

6,836 Sunday midnight

7,142 Dally 6.80 p.m. & 11 p.m..

7,810 Not.eguler ...

7730 Day 11 pm.

B,188 Tues, & Fri, 9 pm-1am 1,230 † Nok!

9,508 Not regular

W.EX.A.F. 1,530 Daily 7 m.

0.020. KL 8 m, Eat &am & 10am.

0,677 Midnight daily

2.F.0. 0 2.A.E.

9,500 Not regular

10,520 Not regular

PLE

31.20 Lindboxes (Holland) F.C.J. 31.29 Sydney

Nairobi (Kanys) 28.6 Bydney 21.3

Bandoeng 20.38 Chelmsford (England) 5.8.1.

24.5 Maglia 28.35 Bobenectady 18.88 Bandoeisg 38.4 Kootwilk (Holland),

Bandoong 17.4 16,0 Bangkok

14.8 Kootwijk (Holland).

13.03 Pittsburg

KLX.R

WAKO.

PLG.

POL

P.L.F. H.8.1.P.J.

P.C.K.

PLE

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ample from the complete range of

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Saturday and Bunday

12,240 Rigby

11,020 Midnight--8 am daily

11,761 7.80 p.m. & 8 am, daily, except

19,850 am. Wed, Fri, Sat.

18,102 Daily 0.80 p.m. to midnight 10,304 Daily 7 p

17.260 Dally 8 pm to midnight

17,751 Sundays 7 pa, & midnight

18,404 Each afternoon.

1:10 290 Daly 4.807 pm

W.9.XI. 21,630 Not regula

[Allowance must be made for "summer-time "in most Euro- pean countries, which is one hour ahead of true time.]

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