PRINTOUT Products Display and Socket Nimo 64 can display 64 different messages in a 1.5-in. panel space. The unit displays the full typewriter keyboard, symbols, image combinations, 5-line messages, etc., with no translation required from coded messages. The Nimo 64 is priced at $29.95. A display kit with the 64-position tube, socket, filament transformer, and power supply costs $49.95. Industrial Electronic Engineers, Inc. 7740 Lemona Ave. Van Nuys, Calif. 91405 Digital Readouts Precision Dynamics is offering six models of digital readouts featuring plug-in decoder drivers. Current limiting and nonglare viewing screens are standard, and the unit allows up to 24 digits in common array. Individual displays feature seven-segment LEDs with 0.270-in. character heights. Precision Dynamics Corp. 3031 Thornton Ave. Burbank, Calif. 91504 Reader /Spooler Model TRS9300 B is a 7lh-in. reel punched tape reader/spooler that reads tape in a standard search-rewind mode at 800 cps. The unit can stop on character bidirectionally at 300 cps, can be operated manually, or by remote control, and reads all standard 5-, 6-, and 8-level tapes without adjustment. Electronic Engineering Co. of California 1601 E. Chestnut Ave. Santa Ana, Calif. 92701 Digital Column Printer The Model 318 is a 3-line/sec, 6- to 18-column low-speed digital column printer that uses a standard format of 10 characters per linear inch and 6 lines per vertical inch. The printer features TTL, zero suppression, fully buffered memory, and serial or parallel input. Price: $595. Datadyne Corp. Building 37 A Valley Forge Center King of Prussia, Pa. 19406 Regulated Power Suplies The OLV-60 series provides 15 334

different output voltages from 4 to 28 V de with current ratings of 12 to 3.5 A. Price: $75. Elexon Power Supplies 19651 Von Karman Irvine, Calif. 92664

Ampex Corp. 13031 W. Jefferson Blvd. Marina del Rey, Calif. 90291 Anderson-Jacobson, Inc. 1065 Morse Ave. Sunnyvale, Calif. 94086

Analog Switches The Series IH5025 through IH5038 series positive input analog switches are priced at approximately $1 per channel. Switching speed is less than 100 nsec, and the family is designed to be driven from TTL open-collector logic (15 V). Each package contains up to four SPST channels. Intersil 10900 N. Tantau Ave. Cupertino, Calif. 95014 Four-Digit ADC CYCON's CY 3735 is a complete four-digit BCD-output ADC featuring 0.01% linearity for $149. The unit is packed in two 2 x 3 in. modules and has 200-microsec speed. A companion unit, the CY 3335, offers the same features with 14-bit binary output. CYCON, Inc. 1080 E. Duane Ave. Sunnyvale, Calif. 94086

Applicon 22 Third Ave. Burlington, Mass. 08103 Bell & Howell 360 Sierra Madre Villa Pasadena, Calif. 91109 Braemare Computer Devices 505 W. 79th St. Minneapolis, Minn. 55420 Burroughs Corp. 5411 N. Lindero Canyon Rd. Westlake Village, Calif. 91360 Canberra Industries, Inc. 45 Gracey Ave. Meriden, Conn. 06450 Chalco Engineering 15126 S. Broadway Gardena, Calif. 90248 Cipher Data Products 7655 Convoy St. San Diego, Calif. 92111

Cassette Cartridge The UDAC records by character on command with five-track parallel format on IJ.-in. tape driven in a true incremental mode with 200 steps per inch. The cartridge holds 300 ft of tape and can be read by character or at slow rate with a speed of 600 steps/sec. UDAC MCA Technology, Inc. 13035 Saticoy St. North Hollywood, Calif. 91605 Miniature de Motor The Escap 26 PL is a miniature de motor with reinforced shaft sold at a reasonable price. Torque up to 3.5 oz in.; speed up to 7,000 rpm; mechanical time constant, 10.6 x 10- 3 sec. The motor is made in Switzerland and has a diameter of 1.024 in. and a length of 1.634 in.

Computer Access Systems 2645 E. Buckeye Rd. Phoenix, Ariz. 85034 Computer Terminal Corp. 9725 Datapoint Dr. San Antonio, Tex. 78229 Conrac (formerly Auricord) Mill Rock Rd. Old Saybrook, Conn. 06475 Datacord, Inc. 795 Kifer Rd. Sunnyvale, Calif. 94086 Data General Corp. Route 9 Southboro, Mass. 01772 Delta Data Systems Woodhaven Industrial Park Cornwells Heights, Pa. 19020 Dicom Industries, Inc. 715 N. Pastoria Sunnyvale, Calif. 94086

Portescap U.S. 730 Fifth Ave. New York, N.Y. 10019 Cassette and Cartridge Recorders Cassette and cartridge recorders are marketed by the following firms:

Digital Equipment Corp. 146 Main St. Maynard, Mass. 01754

Behav. Res. Meth. & Instru., 1972, Vol. 4 (6)

Digitronics Corp. Route 9 Southboro, Mass. 01772

Memodyne 369 Elliott St. Newton Upper Falls, Mass. 02164

Telex 9600 S. Aldrich Minneapolis, Minn. 55420

Dynamic Peripherals P.O. Box 56 Nabnasset, Mass. 01861

Memorex San Tomas Central Expwy. Santa Clara, Calif. 95052

Tri-Data Corp. 800 Maude Ave. Mountain View, Calif. 94040

Dytro Corp. 63 Tec St. Hicksville, N.Y. 11801 Electronic Associates, Inc. 185 Monmouth Pk. West Long Branch, N.J. 07764 Electronic Labs. 3726 Dacoma St. Houston, Tex. 77018 Electronic Processors 5050 Federal Blvd. Englewood, Colo. 80110 Genisco Technology 18435 Susana Rd. Compton, Calif. 90221 Hazeltine/Electronics Div. Cuba Hill Rd. Greenlawn, N.Y. 11740 Hewlett-Packard Calculator Div, 815 14th St., S.W. Loveland, Colo. 80537 Incre-Data Corp. 6405 Acoma Rd., S.E. Albuquerque, N.M. 87108 Interdata 2 Crescent PI. Oceanport, N.J. 07757 Interdyne 14761 Califa St. Van Nuys, Calif. 91401

Mobark Instruments, Inc. 1080-D Duane Ave. Sunnyvale, Calif. 94086 MSI Data Corp. 340 Fischer St. Costa Mesa, Calif. 92627 NCR Main & K Sts. Dayton, Ohio 45409 North American Philips 100 E. 42nd St. New York, N.Y. 10017 Novar GTE 2370 Charleston Rd. Mountain View, Calif. 94040 Peripheral Dynamics 1809 National St. Anaheim, Calif. 92801 Peripheral Systems 215 Little Falls Rd. Fairfield, N.J. 07006 Raymond Engineering 217 Smith St. Middletown, Conn. 06457 Redactron 100 Parkway Dr., S. Dept. 420 Hauppauge, N.Y. 11787

International Computer Products 601 Dooley Rd. Dallas, Tex. 75234

Kybe Corp. 132 Calvary St. Waltham, Mass. 02154 Leach Controls 717 N. Coney Ave. Azusa, Calif. 91702 Lockheed Electronics Co. LT. Route 22 Plainfield, N.J. 07061 MCA Technology 13035 Saticoy St. North Hollywood, Calif. 91605 3M Mincom 300 S. Lewis Rd. Camarillo, Calif. 93010 Behav, Res. Meth. & Instru., 1972, Vol. 4 (6)

Remex Div. of ExCell-O Corp. 1733 Alton St. Santa Ana, Calif. 92705 Ross Controls Corp. 381 Elliott St. Newton, Mass. 02164 Sycor 100 Phoenix Dr. Ann Arbor, Mich. 48104 Sykes Datatronics 375 Orchard St. Rochester, N.Y. 14606 TEAC Corp. of America 7733 Telegraph Rd. Montebello, Calif. 90640

Techtran Industries, Inc. 580 Jefferson Rd. Rochester, N.Y. 14623

Tycome Systems Corp. 75 Hamburg Turnpike Pompton Lakes, N.J. 07442 Univac Div. of Sperry Rand 322 N. 21st si., W. Salt Lake City, Utah 84116 V ari -Systems 80 Skyline Dr. Plainview, N.Y. 11803 Victor Comtometer Corp. 3900 N. Rockwell St. Chicago, Ill. 60618 Wang Laboratories, Inc. 836 North St. Tewksbury, Mass. 08176 Xebec Systems, Inc. 366 San Xavier Ave. Synnyvale, Calif. 94086 Signal Transmission Cable The Ansley low-crosstalk signal transmission cable is available as assemblies or as bulk cable (flat cable). Ansley Electronics Corp. Old Easton Rd. Doylestown, Pa. 18901 Aquamex Aquamex is an instrument for measuring and registering the locomotor activity and behavior of fishes with a minimum size of 10 mm, or of other water animals with a minimum size of 50 mm. The sensor is a plastic/glass frame containing two ultra sound crystals, one transmitter, and one receiver. The frame contains two air mirrors, and the sound is bounced backwards and forwards in the frame, forming a measuring wall. When a fish passes through the frame, it reflects and diffracts some of the ultrasonic signal. This is registered by a receiver, and a pulse is given to a counter indicating the number of passages. The time that the fish remains in the frame is also measured and taken to a second counter, which shows either time of the last passages through the frame or nonaccumulated time of all passages through the frame. It is thus possible to estimate the speed of the last passage, or the average speed of all passages, by dividing the elapsed time by the number of passages. Aquamex is delivered without aquarium. The frames are simply 335

inserted in the existing aquariums. Excess space around the frame is covered with Plexiglas, and Plexiglas should be specified when ordering. The unit can be compensated for use with fresh or salt water, clear or polluted, of different temperatures. The use of two units makes it possible to identify direction of swimming. A.B. Farad Stockholm Nyborgsgrand 12632 Hagesten Sweden

or LKB 12221 Parklawn Dr. Rockville, Md. 20B52 Shielding Tapes New Scotch Brand tapes with embossed metal foil backings provide an easy, low-cost way to apply lasting EMI shielding in applications up to 12 GHz. Applied to a copper substrate, over a % x 23,4 in. open slot radiating at 143 MHz, Switch X-1245 tape holds the insertion loss level at a steady 65 dB. Insertion losses are equally consistent on steel, aluminum, and cadmium, ranging from 35 to 55 dB. Easy to apply, the shielding tapes end the need for plating, painting, or other shielding methods in many applications. Scotch Brand V-1245 has an embossed copper foil backing that permits solder connections. Scotch Brand X1267 has an embossed aluminum foil backing. DM & S Div.

3M Company St. Paul, Minn. 55101

Econ-O-Tape Econ-O-Tape is a weldable contact strip produced in long-length coil form by rolling and shaping a solid or clad contact material combination. Attachment by welding is permanent, and the manufacturer claims that it will not loosen due to temperature expansion and contraction. Engehard Industries Pine and Dunham Sts. Attleboro, Mass. 02703 Function Generator The new Series 500 combines the advantages of a function generator and a lab amplifier. The unit produces a spectrum of multifunctional signals and provides a 65-MHz amplifier with < 10-nsec response. It can be used separately or with any of the Oilteeh 5- or 10-MHz waveform generators to do signal summation, modulation, and other jobs. 336

Oiltech 19535 E. Walnut Dr. City of Industry, Calif. 9174B Digital Printers The new Model 415 digital printer offers from 7 to 21 columns of line capacity. Floating decimal point, red/black printing with selection by numerical field, zero suppression, "print control" over three-input channels, and a remote control option. Speed is 3 lines/sec, and printing stock is paper or fanfold. The 415 measures B% in wide x 7% in. high x 17 in. deep. Price: 11 columns, $549; 14 columns, $649; 21 columns, $B29. Leasametric

B22 Airport Blvd.

Burlingame, Calif. 94010 Random-Access Slide Projector The ESP-2000 AV random-access slide projector has an access time of 4 sec and a 4,OOO-h motor. The plastic tray accepts 100 slides in standard 2 x 2 in. mounts. The projector focuses automatically after the first slide is brought into focus manually. Cost: $499. GAF Corporation Audio/Visual Dept. 140 W. 51 St. New York, N.Y. 10020 Sound Level Meters The RCA WE-130A sound level meter has a range of 70 to 110 dBA, with an "A "-weighted meter frequency response, a slow response time, and a ceramic-omnidirectional ceramic microphone element. The unit operates on four AA penlite batteries and measures 6-7/B in. long x 3 in. wide x 1-15/16 in. deep. The weight is 3 lbs and the price is $75. Herbach and Rademan, Inc. 401 E. Erie Ave. Philadelphia, Pa. 19134 PDP-8 Memory Signal Galaxies PDp·B plug-compatible memory is a low-cost alternative to the DEC PDP-B computer memory. The unit plugs directly into the bus connector blocks in the DEC computer chassis and can be used as an add-on or as a complete substitute PDP·8 memory. It operates directly from the PDP-8 internal power supply and has less power drain than the comparable DEC memory configuration. A I-year warranty policy includes replacement. Prices are as follows: First 4K memory for PDP-B/E with 4K memory is $1,795, with a reduction to $1,200 for each additional 4K (adding 4K to an 8K PDP-B/E costs $1,630); first 4K for a

PDP-B/i with 4K memory is $3,380 ($1,200 for each additional 4K). Memories are available also for the PDP-ll and the Honeywell DDP-516 and DDP-316 computers. Signal Galaxies, Inc. 6955 Hayvenhurst Ave. Van Nuys, Calif. 91406 Minicomputer Rentals Rental Electronics, Inc., of Gaithersburg, Maryland, is offering Data General Nova-line minicomputers for rent and lease under the following plans: (1) One-month to I-year rentals, (2) 1- to 3-year leases, and (3) rental conversions that allow rental payments to be applied against the purchase. According to Rental Electronics, Inc., a NOVA 1200 with BK memory (16-bit words), teletypewriter, and interfacing rents for $768 per month. Lease rate is $392 per month on a 12-month basis. Psychological Instruments Coulbourn Instruments, Inc., is marketing instrumented laboratory systems that appear simple in configuration and well systematized in interrelationships of modules. The analog, audio, and digital functions are well integrated for correlated psychological and physiological research. For example, straightforward operant work is programmed with digital modules, but it is possible to build a polygraph right on the rack by using a two-channel strip chart recorder and control panel. Analog information may be input into the digital system from the S7 series via the VCO, ST, or AD converter, and there is a full complement of audio modules. The system may be powered by either Grason-Stadler or Lehigh Valley Electronics power supplies. Since a frame capable of holding 16 modules is priced at $25, a second source supply and a wider range of modules to choose from may be of some benefit. Technically, the units have COS/MOS logic, buffered for 12 V. This provides 5 V noise immunity and 15·50 load fanout with low power supply loading. Typical prices: adjustable Schmitt trigger input, $85; voltage controlled oscillator, $225; 10·bit AID converter, $325; voice-actuated switch with microphone, $225; dual Arid/Nand gate, $32; binary scaler, $32; 8-bit up/down counter, $125; 5-unit power driver, $75; bridge amplifier, $250; EMG, $300 (same price for EEG or ECG); noise generator, $75; adjustable tone generator, $90; two-channel analog recorder control, $175: and four-digit electronic counter display,

Behav. Res. Meth. & Instru., 1972, Vol. 4 (6)

$250. The company also offers two self-contained EMG bio-feedback systems priced at $275 and $600. Coulbourn Instruments, Inc. Box 2551 Lehigh Valley, Pa. 18100 Teletype-Compatible Terminal The Model 3501 Asciscope terminal offers the user editing facilities and communicates at either 110 bits/sec (Teletype compatible) or 300 bits/sec. The terminal has a memory capable of storing the entire screen display (12 lines of 80 characters each). A 5 x 7 dot matrix forms characters. Editing can be done on a line-by-line basis before transmission. Interfaces are included to printers and to external 1,200- and 2,400-baud modems. Purchase price is $2,195; maintenance cost is $20 per month. ITT Data Equipment and Systems Div. East Union Ave. East Rutherford, N.J. 07073 Minicomputer The new Texas Instruments Model 980A general-purpose computer has the following standard features: 16-bit word; hardware, multiply/divide with 16- or 32-bit add and subtract; 750-nsec add immediate; 5.20-microsec multiply; 750-nsec fully memory cycle time; bit/byte/word/byte string data addressing; memory parity; power fail/auto restart; power supply to support 65K memory; memory biasing; I/O bus with 4 ports basic (expandable to 14 in basic chassis, 256 overall); main chassis memory expandable to 32K, up to 65K with a memory expansion unit; switch-initiated ROM bootstrap loader; direct memory-access channel; 4 priority interrupts (expandable to 64); 98 basic instructions; 9 addressing modes; and 8 working registers plus status register. A pregenerated standard software system is supplied which allows the user to generate custom system software. Additional software includes: symbolic assemblers and cross-assemblers for IBM 360/370; FORTRAN IV; link and source editors; modular executive control routine, including disk management; TI language translator to extend FOR TRAN or create special application languages; and maintenance, debugging, and utility programs. Prices of the unit: CPU with 4K memory, $3,475; 8K memory, $4,975; 16K, $7,975; 32K, $13,975. Prices do not include cabinet. Computer Products Marketing Manager Texas Instruments, Inc.

P.O. Box 1444 Houston, Tex. 77001 Cassette Storage SYstem Ross Controls of Newton, Mass., has announced minicomputer-interfaced storage systems for the DEC PDP-8 and the Computer Automation Alpha 16. The Series 1100 cassette recorder uses standard Philips cassettes and a reel-to-reel-servo-controlled drive mechanism for highly reliable data recording and transfer and tape interchangeability. Typical price is $1,150. PDP-11 Tape Controller Information Products of Houston, Tex., is marketing the Series 1X15 tape controller, which functions as a complete memory subsystem or as a controller interface for PDP-11 minicomputers. The unit provides data transfer control between the PDP-II and up to four 7-/9-track transports with minimum software intervention. The controller comes with I/O driver and diagnostics routines. Price: $3,040. Microdrive for Neurophysiology The new Wells motorized hydraulic microdrive consists of a logic type of electronic controller, a quiet brushless de stepping motor with precision speed reducer, and either of the two hydraulic systems used in the manually operated Wells hydraulic microdrives. The No. 3-0660 unit has a standard master and slave cylinder; the No. 3-0665 has a miniature master and slave cylinder. The hydraulic systems of either unit are interchangeable. Features include a digital display of stepping counts (each step equals 1 micron), a pulse output for recording the instant and direction of stepping, an internal mode for con tinuous stepping at infinitely variable rates from 2% to 300 steps/sec in either direction, a single pulse mode for bidirectional manual stepping, and an external input accepting logic signals, which permits the unit to be driven by either a programmable signal generator or a computer for time-displacement studies or by a computer for seeking specific types of signals. Total backlash is advertised as normally less than 5 microns and in a given unit will remain essentially constant. Price: Standard unit, $1,525; miniature unit, $1,625. Trent-Wells Mechanical Developments Co. 8120 Otis St. South Gate, Calif. 90280 IC Timer The Model 555 is a standard IC timer with many applications. The 555 functions interchangeably as a

Behav. Res. Meth. & Instru., 1972, Vol. 4 (6)

time-delay oscillator, pulse detector, or power modulator. It times 4 microsec through 1 h and has completely resettable time delays. Externally triggered, the unit will either free run or latch in adjustable duty cycles from 50% to 0.01%. Timing can be changed 10:1 with control. It operates from 5 to 15 V with only a 1% change in timing. Output can source or sink 200 rnA. Applying the 555 requires only a resistor and capacitor; it can operate from a single power supply. The unit is a single 8-pin dual in-line circuit and is low in cost. In orders of 100 or more, the price is 75 cents per device. Signetics-Linear 811 E. Arques Ave. Sunnyvale, Calif. 94086 12-Bit D/A Converter Computer-controlled CRT display systems require D/ A converters that are fast and accurate. Hybrid Systems has introduced a converter with both characteristics as well as a relatively low price ($125 each). The DAC 395-12A has a settling time of 50 nsec, 12-bit resolution, and ±0.0125% linearity. The unit is packaged in a 2 x 2 x 0.4 in. module. The DAC accepts either straight binary or offset binary input codes and is TTL-compatible. The unit is said to be the fastest modular 12-bit DA V available as of this date (September 1972).

Hybrid Systems Corp. 87 Second Ave. Burlington, Mass. 01803 Pushbutton Switch The DVR-2000 series pushbutton switches, when non illuminated, present a black band at the base of a colored recognition cap. The switches are available in push-lock/push-release and momentary-actuation types with 1-4 Form C contacts. Price: $1.50 for 1 Form C; $2.50 for 4 Form C. Switchcraft, Inc. 5555 N. Elston Ave. Chicago, Ill. 60630 Paddle-Handle Switch The subminiature J-60 paddle-handle switch offers snap action and an enclosed case. Overall length is 0.715 in.; above the panel, height is 17/32 in. The switch is available with single to four-pole double-throw configurations. The advertised minimum electric life is 100,000 make-and-break cycles. C & K Components, Inc. 103 Morse St. Watertown, Mass. 02172 337

Relays Magnecraft offers Class 388 general-purpose relays in covered or open style units with a wide choice of ac or de coil voltages and SPDT to 3PDT, 10-A contacts. All relays have three-way pierced terminals, i.e., plug-in, tab, or solder. Sockets with quick-connect, solder or PC terminals are available for plug-in use. Magnetic Electric Co. 5575 N. Lynch Ave. Chicago, III. 60630 CRT Data Terminal VST-1200 screen size is 80 in. (standard 12-in. tube). Capacity is 1,296 characters. Display page: 72 characters/line, 18 lines/screen. Character size: 0.20 x 0.10 in. Code: Full 128-character ASCII generation and recognition. Refresh rate: 60 Hz. Display: 64 and 96 characters. Parity checking and generation: Even, odd, or none. Keyboard: Teletype Model 33TZ, plus standard 10-key adding machine, plus 10 control keys or 37 Vz. Cursor: Cursor home control up/down or left/right cursor may be moved one space at a time or slewed Non Destructive Cursor. Baud rate: input/output rates of 110, 150, 300, 600, or 1,200 baud are available (2,400-baud optional). Output hard copy: Information may be printed with a Model 33, 35, or 37 Teletype, NCR-EMT2, or other compatible printer. Video output: Composite video signal is compatible with most standard closed-circuit TV systems, allowing use of large-sized screens and multiple displays. Price: $1,795. Video Systems Corp. 7300 N. Crescent Blvd. Pennsauken, N.J. 08110

Briefs X-Y Recorders Honeywell X-Y recorders are now made and sold by Esterline Angus, P.O. Box 24000, Indianapolis, Ind. 46224.

Biobelt Biobelt is a long-distance electrocardiogram device developed by Lockheed Missiles & Space Co. The unit detects heart and body temperature signals and feeds them in sequence to a comment unit (after amplification), where the signals are converted to binary form and transmitted to a central unit. A CRT at the central unit reads the information at a rate of 10-5,120 samples/sec. Biobelt is worn about the waist as a belt. 338

Company Change Nicolet Instrument Corporation has acquired Federal Scientific Corporation. Federal Scientific manufactures real-time spectrum analyzers and signal correlators. Its products and markets complement Nicolet's signal-averaging instrumentation. Panel Meter California Instruments of San Diego, California, will soon introduce a 3lh-in. digital panel meter that is only lh in. thick and will sell for about $115. The unit uses LED displays and requires no more of a panel cutout than is needed for a cable. Lehigh Valley Electronics Lehigh Valley Electronics is now part of BRS-Foringer, Inc. Swapping Instrumentation Information Aperiodically, the Printout section of this journal will publish announcements judged to be useful concerning the availability of used psychological instruments, requests for information, departmental or individual exchange requests, etc. Address information to the Editor.

Notes Automatic measurement of food competition in the laboratory rat DOMINIC J. COSTANZO* and DAVID HOTHERSALL The Ohio State University Columbus, Ohio 43212 The purpose of this paper is to describe an apparatus for measuring food competition in the home cage of the laboratory rat. Although this apparatus was designed to measure social dominance as indicated by priority of access to a food incentive, it might also be used as a measure of home-cage food competition over long periods of time. APPARATUS Figure 1 is a perspective view of the rats' home cage (double Wahmann suspended rodent cage, LC-75/B) containing the apparatus. The device divided the home cage into two equal *This research was conducted while the senior author was on a leave of absence from Muskingum College, New Concord, Ohio. Reprints may be obtained from David Hothersall, The Ohio State University Research Center, 1314 Kinnear Road, Columbus, Ohio 43212.

areas, each occupied by one animal during the food competition period. A circular food cup with a lid containing a 1-5/16-in. opening (Wahmann LC-75/B) was clipped to the center of the front wall of the cage with a holder (Wahmann LL-75/B). To reach the powdered rat chow in the food cup, the rat had to deflect the hinged gate, which was designed so that only one rat could feed at anyone time. In addition, the movement of the gate was limited so that the rats could not move from one side of the cage to the other. Figure 2 is a scaled schematic drawing of the device showing the major details. Adjustable V3-1 microswitches with JV-26 levers (Minneapolis-Honeywell) were. mounted at "A" on either side of the gate. Inset"AI" shows a top view of the mounting for one of the two switches. The microswitches were adjusted to operate at the slightest deflection. These were connected through pulse formers to counters that recorded the number of gate deflections and the number of times a given pair alternated control of the food cup, and through relays to timers that recorded the duration of each rat's deflection. So, the number of occasions each rat controlled the food cup, the number of alternations of control, and the total time in control could be recorded. "B" shows the top-hinged gate, which was constructed of clear Plexiglas with a I-in-diam Lucite rod at its base to cover the opening of the food cup lid. "D" indicates the 2-in.-wide aluminum angle plate (14 gal, which was screwed onto the 21h-in.-wide Plexiglas beam (C) from which the instrument was suspended. The angle plate (D) engaged the back notch of the rodent cage and served to mount the testing device. At the front, midway between "C" and "B," a slotted plug was wedged into the wire mesh of the cage wall to firmly engage "E." This served to position the gate (B) over the food cup opening. The handle end of a spring-loaded clothespin nicely served this function; its protruding end also served to hold the wiring away from the front of the cage. The barrier labeled "E" was constructed of l/B-in. black Plexiglas and was suspended from a centered groove in "C." Each microswitch assembly (A) was protected by a Plexiglas cowling, and the wires from the microswitches exited via plastic tubes and converged into a common groove in "C." This groove was covered with clear plastic tape. Four inches from the front of the apparatus, the wiring terminated in a standard male connector. The

APPLICATION apparatus described

here

Behav. Res. Meth. & Instru., 1972, Vol. 4 (6)