HEALTH SCIENCES LIBRARYMcMASTE? U'IssVERSITY

I`4

MAY 9 '7;

2 Mlay 1975

Vol. 188, No. 4187

....... ...,,i4 -.-,,

Xij...I..-

We want to be useful ...and even interestingCommunication by microscopeBesides looking throug_,h a miicroscopC. x on c,an taLke picttures w ith it.Y'oLu miax xx ant the pictnLres only as a r-cor-d ot xx hat xyon sav. Or xonmrIoTht xx ant thenm for comnininicatilln to othCe-s xonr thonghts on xvhaton a If-so nLnless OLI fleel ther-e is nio I-ooIml or inmprox cnent

inI x'onlr photomicrographx -- Kodlak PLnblicaltron P-2,-` "Photographythrotlrh the Microscope, mna pror c hclpfuLl. In the conLrse of tellinghow to aet the most ouLt of oLur produlCtS. it dliscuLssCS things xve diontcxen provide. For cxample, Kohler illuIminationl.

Therc are microscope illuminators (in 10th-gradc hiologx labs, per-haps) th'at clo not tise lenses to dlirect the light into the stubstage con-denser. In that casc, don't xxorrx ahonLt Kohler illum11ination bcCau,lsCxVOLI cant haxa it, nor canl VOLn cxpcct as much lxing poxx ci firom achigh-laperturc objectixe as theory predicts. If xyon haxve prorecssed bc-yond sLrch cquipnment, car-Cltll1 retFad the ma.nuLal that coImcs wxith the

mnicroscopc. Hopc that ifthe maInLut'actuLrCerS sLI"gCs-

FILM PLANE [i tions ar-c folloxx cd Kohler-illUmination xvill be mnain-

tamined, cxven if that tnamiec isCAMERA OR \___,__ ot Lusecd. A brain, cotncct trat-FILM HOLDER \ \ing its attention otn the ascinlating

cetails of thc specimiCeI, learins toSHUTTER Sigore enneSs ot illuminaIltionEYEPIECE EYE LENS and other off-Kohler etfects. Not

ebing that smart, the photographicEYEPIC

process faithtflllx renrders thcmand miaiay vcxl cxaggerate themil

tc the point of losing xxvhat'simiportant in the suLhjecct.

It can he hbadeInouL(gh to roh the

BODY TUBE .auLdicence of faithin the cleverncss

FXIT PUPIL . \ofthe conm-OF OBJ ECT V EI mntincator.OBJECTIVE J

STAGE

CONDENSER

APERTUREDIAPHRAGM

FIELD DIAPHRAGM

MIRROR

BASE- /.:

COLLECTOR LENS

LAMP

THE KOHLER ILLUMINATION PRINCIPLE

The collector lens gathers light from the emitting source, whether lamp fila-ment or arc. Source should be in sharp focus at the aperture diaphragm. Itsimage doulc be centered wxith that diachragmr and it should be large enorghto extend just a bit beyond the widest opening. If it is much larger. you are

wasting light. If it is much smaller, you may be losing some of the resolvingpcwer the objective could be delivering.Tevo further imageS of the light sourcexv' be formed, one by the condenser and objective in combination and thesecond by the eyepiece. If an image of the aperture diaphragm and within it

+i- r~a,scIhe rt r 'do %vtt the rlane tf the shutterthe relaved image of the cht scLurce co ncid ihtepn otesutrarnd are No larger than tre shutter opening, the film is getting the full benefitof the light to keep down problems from long exposures, and it is seeing therrnst of t'e s:ec mex s strL cture and the least of the light source's structure

She must have gone to the dentist

-an c ro m at ic

Hesiectec UV oUiy

uv-excitui visitie Tluorescence

reaeteuiaU IF Uom1y

Visible-excited IR luminescence

Since the uLinerCl took place as lonig ago as 600A.D. in xxhat the palcfaces later nameed JerseyC'ouLntV, Illinois, the archaeologists took thelibeirts of distUrhing the lady's rest. Their in-x estigations bring ncNx respect for the culttLreof her people. 1TherapeCLtic cdenltistry, it seenms,xxas not heyond their technological capability.I-o cx-lilt ate the cvidencc tor th'at, send for the

articlc "MLIlti-spectrutm Invcsti-o ation ot Prehistoric Teeth." ItIaorc intcrcsted in the photo-, raphic imiethods thani in the find-mis, gct Kodlak PtublicationM-27, "Ultraviolet and Fluorcs-cenCce Photography.,

KODAK Directory of Products and Services for the Health Sciences is available free feroDept. 55M, Kodak, Roc/rester, N.Y. 14650, as is the article o;r tire eidenicc fo(- prer.'storridetitistry. Kodak Publications P-2 anid M-27 cant be ordered from phloto dealers, sore book-rstors, or cat $3.25 atnd $2.25, respectiively, fri-om ou:tr Dept. 454. (Prices sUbj(ct to c'batrgew ithiout tiotic'e. Please add applicable taxces.)

AAAS

announces

THE '75 MEMBERSHIP DRIVE

A t a time when science and its role in human affairs is being scrutinizedmore closely than ever before . . . when inflation and sharply rising

costs in all areas are affecting organizations and institutions as well asindividuals ...

We at AAAS are reaching out ...

for new members ...

for new ideas...

for a wider base of support ...

so that we can remain a dynamic force within the scientific and technicalcommunity!

AND WE'RE COUNTING ON YOU,OUR ACTIVE MEMBERS, TO HELP!

In the near future you will receive a letter from AAAS explaining the '75Membership Drive and asking you to take just a few minutes of your timeto participate.

* If you are one of our active members ...

* If you have more than a casual interest in AAAS, its progress andgoals . ..

* If you want to do something to help . . .

then watch for the arrival of our letter and take part in the '75 MembershipDrive!

AMERICAN ASSOCIATION for the ADVANCEMENT of SCIENCE1515 Massachusetts Avenue, N.W.

Washington, D.C. 20005

MEASUREMENT,COMPUTATION: changing things for the better

STIMULUS

A new standard communicationslink that facilitates conversationamong instruments.

It wasn't long ago that all instruments were,in human terms, totally deaf and dumb. Theycould not hear instructions so you made them dotheir job by setting knobs and switches. Andwhen the job was done, they could not tell youthe results; the only way to find out was to read,and then analyze, their displays.Many instruments have since learned to "talk."

On command, they can output measurement re-sults and transmit them remotely in code. Moreand more are being equipped to "listen": sendthem prearranged signals and they can programtheir own controls, remotely. Add a control func-tion to such instruments-to tell them when totalk and when to listen-and they can com-municate with each other automatically.

This sounds easy, but it hasn't been. Althoughthe three basic elements for automatic instrumen-tation systems-talkers, listeners, and control-lers-are readily available, one who sets out todesign and assemble such a system quickly runsinto severe frustrations. The different elementsare rarely compatible; more often than not, theyuse different logic, speak a different language,and interconnect with different hardware.Avoiding this electronic Tower of Babel is

what the Hewlett-Packard Interface Bus (HP-IB) isall about. A standard interface system, the HP-IBforms a basic communications link that allowsinterconnected system components to communi-cate effectively, in an orderly and unambiguousmanner. The interface system involves muchmore than the standardization of interconnectingcables; it also defines the interface logic capa-bilities within the system instruments, the scopeof the data codes used on the interface, and thetiming and control techniques for exchangingmessages.

MEASUREMENT

To talk or to listen: never a doubt.In the HP Interface Bus, all system devices are

exposed to all system communications. But adevice can neither send nor receive a messageunless told to do so by the system controller: atany given time, it can be either a talker or alistener, but not both. Listeners receive program-ming data from a controller or measurement datafrom talkers; talkers send measurement data tolisteners. There can never be more than one activecontroller or one talker at the same time, but therecan be as many as 14 concurrent listeners.Depending on its capabilities, a device may

play more than one role at different times. A cal-culator or computer, for example, can be talker,listener, or controller; a programmable digitalvoltmeter alternately talks when it outputs itsmeasurement and listens when it's being pro-grammed; a paper punch can only play the roleof listener.The bus: a common interconnection.

All system devices are interconnected on acommon set of 16 signal lines. Eight of theselines form the data bus which carries all datamessages bidirectionally between talkers andlisteners, in bit-parallel byte-serial fashion. Thetransfer bus uses three lines to ensure that data isinterchanged only from the intended talker tothe designated listeners, through an interroga-tion and reply sequence. The remaining five sig-nal lines constitute the control bus, by which thecontroller directs an orderly flow of informationacross the interface, sending commands to thedevices and receiving service requests fromthem. Although system control is always dele-gated (never assumed), it may be shifted fromone system device to another.HP-IB simplifies systems, small or large.An HP-IB system can consist of one talker, one

listener, and no controller; for example, a counterand digital printer for semi-automatic data log-ging. At the other extreme, a completely auto-

DATA

STORAGE & CONTROL

matic system may include as many as 15 instru-ments possessing stimulus, measurement, dis-play, storage, and control capabilities. Whethera calculator, computer, or the processor of a"smart" instrument, the controller operates theentire system through an interface connection (asingle I/O card)-an obvious economy comparedto non-bus systems that require one I/O card foreach instrument.System configuration: fundamental problemssolved.Although the HP-IB does not provide instant

systems, it does solve the fundamental interfaceproblems that have plagued instrumentationsystem designers and users until now. Designers-no longer need to invent custom interfaces foreach new product; users no longer need to famil-iarize themselves with an interface unique toeach new product. Cable and connector problemsare minimized by the use of a simple, passivecable interconnection system.

HP-IB protocol allows the designer to assigntalk and listen addresses to each device to suithis purposes. Each address is set at the deviceto any desired value, through a switch on a rearpanel, jumper wires on a PC board, or other con-venient means.The HP-IB imposes minimal functional re-

strictions on data transfer between a talker and alistener. For example, data bytes may consist offrom one to eight bits. Once a device is addressed,data can be transferred using any coding andformat convention appropriate to the application.The most commonly used codes are the printablecharacters of the ASCII code set, and the number

HEWLETTI PACKARD

Sales and service from 172 offices in 65 countries.Palo Alto California 94304

representations are typically FORTRANcompatible.Minimal timing restrictions are imposed on the

data rates by the HP-IB. Data is transferredasynchronously at a rate that suits the devicesinvolved; burst rates of 1 megabyte per second arepossible over limited distances. Data may betransferred directly between devices, thus re-ducing message traffic on the bus.More than a theory, HP-IB is a reality now.

Within Hewlett-Packard, the common inter-face concept has already been incorporated intoa growing list of more than 25 instruments andaccessory products as well as our computers andprogrammable desk-top calculators. Addition-ally, the HP-IB is our implementation of newIEEE Standard 488-1975-and it has served as amodel for the IEC Recommendation recentlyreleased for ballot among member nations. Thusthe possibility exists that this concept will be-come internationally applicable to the inter-facing of instruments, without regard to manu-facturer or nation of origin.

Obviously an idea whose time has come, thecommon interface is here now, still another as-pect of the new measurement technology that istaking shape at Hewlett-Packard.

For more information, write to us. Hewlett-Packard, 1507 Page Mill Road, Palo Alto,California 94304.

Nail to: Hew!lett-PJackard, r507 I'age lvlill Rtoad,. Palo Alto, (C^ 34$)

Please send me fLirther inforniation on theFiev.-lett-Pi"ackard Interface( [tLIS.

Naine T e

C,omp;anlyAddress

StCitx State Zip

00544

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For the past six years, AAAS hasrecorded selected symposia at itsannual meetings, many of whichmay be within your professionalfield of interest. This fine collec-tion of audiotapes not only servesto enlarge the audience reachedby our annual meetings, but alsoserves as a valuable aid to edu-cation, particularly in classroomor seminar-type settings. Whynot send today for your freecatalog of audiotapes, arrangedby subject category?

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