Analog Computers

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EAI Report No. 014 — March/August 1968 (4th Year): Product News and Announcements

This document is an English translation of the original German-language EAI-Report Nr. 014, 4. Jahrgang, März–August 1968, published by EAI Electronic Associates GmbH, Aachen, West Germany.

EAL 380 — New Computer Capacity

At this year’s IEA exhibition in London, 13–18 May, the new Analog/Hybrid computer EAL-380, jointly developed by EAI in the USA and England, was presented. It is a fully transistorized 10 V desktop computer in which the analog section and parallel logic are combined in a single console. The experience gained in building well over 2,000 desktop computers benefits this device, which combines the low cost of a desktop computer with the technical characteristics of more expensive systems.

Key specifications of the EAL-380 Analog/Hybrid Computer:

  • +10 V reference voltage
  • 36 computing amplifiers
  • 32 potentiometers
  • Many nonlinear components
  • Optical and acoustic overload indication
  • Electronic mode control EMC/LMC
  • Built-in parallel logic with universal registers, AND gates, BCD counters, differentiators, etc.
  • Accuracy: ±0.01% (linear computing components)
  • Bandwidth of computing amplifiers: 400 kHz (at 20 V peak-to-peak, 10 kΩ input and feedback resistance)
  • Removable patchboard for analog and logic sections

The computing components, constructed using plug-in card technique, permit individual configuration and continuous expansion up to full capacity. The computer can of course also be used as a classical analog computer without the parallel logic.

Among the standard components provided are: wideband computing amplifiers (400 kHz, 3 dB), individually controllable integrators, track/store units (analog memory), bipolar parabolic multipliers (accuracy ±0.075%), sin/cos function generators, variable diode function generators with adjustable breakpoints, electronic comparators, function switches, limiters, universal registers, counters, gates, and flip-flops.

The mode control of the integrators and track/store units is done individually or in groups, either from the parallel logic or from the operator panel (LMC–EMC). This is particularly advantageous for iterative computing. The timer can be set to values between 1 ms and 9.9 s for “compute” and “initial condition.” The breakpoint and slope of the variable diode function generators can be conveniently adjusted using ten-turn potentiometers.

The clearly arranged operator panel contains the component selection system, mode control, indicator displays for comparators, function switches and flip-flops, a 4½-digit digital voltmeter, and the overload indicator window.

Parallel operation of multiple machines and the possibility of coupling with all EAI computers enable multiplication of computing capacity.

EAI 690 — Hybrid System

The EAI-690 Hybrid System — consisting of the Analog/Hybrid computer EAI-680, the digital computer EAI-640, and a corresponding interface EAI-693 — is operating at the EAI European Hybrid Computing Center of EAI Electronic Associates Inc., European Division, 116–120 Rue des Palais, Brussels 3, Belgium.

A staff of experienced specialists is available for the analysis and solution of analog, digital, and hybrid computing problems.

EAI 680 Analog/Hybrid Computing System — New Developments

In EAI-Report No. 009 of October 1966, the larger Analog/Hybrid computer EAI-680 was introduced. Recently, the 100th (one hundredth) computer of this type left the manufacturing plant in the USA! EAI, continuously working to expand the technical capabilities of its systems, has developed new components and add-on devices presented below.

I. Computing Amplifiers with Short Recovery Time After Overload

The EAI-680 computing amplifiers are now equipped with an amplitude limiter that, when the reference voltage is exceeded, limits the amplifier output voltage to ±12 V within a few microseconds. This prevents saturation of the overloaded amplifier and ensures linear operating characteristics below the reference voltage. The recovery time of the overloaded computing amplifier then falls in the order of magnitude of the switching time of the limiter. Independently of this, as soon as the reference voltage is exceeded, an immediate optical and acoustic overload indication is given, and a logical overload signal (OU) appears at the problem board. This signal can be stored or used to stop the computing process (ORH). The electronic overload limiter is implemented as a small printed circuit and is installed from now on in all computing amplifiers of the EAI-680.

II. Integrators with 3 Electronically Controlled Operating Modes

The type of switching of integrator operating modes is an important characteristic in analog computing. When solving boundary value problems, the integrators must be switched from the initial condition (IC) state to the compute (OP) mode as rapidly as possible, so that switching errors remain small in high-speed computing. This can only be achieved by electronic mode control (EMC).

In the standard 680 integrators, switching between IC and OP, or OP and IC, is done electronically with a switching time of 1 µs, while switching from OP to hold (HOLD) or vice versa is done via relay (switching time 2 ms).

In the diverse applications of the EAI Analog/Hybrid computer 680, there has been an increasing demand to switch between all three operating modes (IC, OP, HOLD) at high speed. To meet this requirement, EMC integrators are now available that, using four FET gates, can switch between the three operating modes with an accuracy of 0.01% and microsecond switching times, and exhibit low-drift behavior in the “hold” state.

In the “compute” state, a small storage capacitor (5 nF) tracks the integrator’s output voltage. When the “hold” state is triggered, a 10 µF capacitor is switched into the integrator feedback with a 10 ms delay, so that the computed value can be stored drift-free for an extended period. The new EAI-680 integrators can be used for three-mode computing cycles without using additional computing components, since they fulfill the computing functions of EMC integrators and analog memories on their own.

III. Multiplier Plug-In with 3 Computing Amplifiers

The new EAI-680 multipliers additionally contain 3 amplifiers alongside the multiplication network. This allows the complete execution of multiplication within a single plug-in without using additional amplifiers for inversion. Using the multiplier plug-in, the following computing operations can be performed:

  1. Multiplication
  2. Division
  3. 2 squarings
  4. 2 square root extractions
  5. 1 squaring and 1 square root extraction

The use of integrated circuits has enabled a compact design while maintaining the general technical characteristics of the Analog/Hybrid computer 680. The new multiplier plug-ins can extend the computing capacity of the EAI-680 by 2 amplifiers per multiplier (up to a maximum of 48 additional amplifiers total), raising the total EAI-680 computing capacity to 204 computing amplifiers.

IV. Expansion System for the EAI-680 Analog/Hybrid Computer

The expansion of the EAI-680 with an add-on device is now possible. The EAI-680 expansion system is self-contained and includes the power supply and the necessary control and I/O facilities for accommodating additional analog and logic computing components. Overload indication, reference voltage, selection systems, mode control, and a problem board are provided for each expansion unit, so the whole system can be used alone or in conjunction with a 10 V or 100 V reference voltage analog computer.

The expansion system consists of 6 expansion units, configured in 19-inch plug-in form or in groups of 20 EAI-680 computing components. A separate problem board is provided for each expansion unit. Wiring and shielding are implemented such that the dynamic and static characteristics of the main computer are maintained.

The add-on device consists of a combination of the following facilities:

  • Resolver
  • Central coupling system
  • 10/100 V adaption unit
  • Additional analog or logic section
  • Standard 19-inch plug-in

1) NRS Resolver System

The electronic resolvers of the EAI-680 system consist of computing amplifiers, integrators, multipliers, and sin/cos diode function generators, connected as either ±180° resolvers or continuous resolvers. The outputs of the resolvers, up to 6, appear at the EAI-680 problem board. The resolver system is divided into resolver pairs, each pair having its own problem board.

The following resolver operating modes are available:

  • PR1: Polar-to-Cartesian conversion of 1 vector
  • PR2: Polar-to-Cartesian conversion of 2 vectors with the same angle theta
  • RA: Axis rotation
  • RP: Cartesian-to-Polar conversion of 1 vector

The control of the resolver circuits can be done directly from the main computer or individually on the resolver problem board. The resolver expansion unit can accommodate a maximum of 20 computing plug-ins, assembled in 2 groups as follows: 1 integrating summer, 2 sin/cos DFGs, 4 multipliers, 1 resolver control plug-in, 1 switch plug-in, and 1 plug-in with 8 inverters. All these computing components can be used individually.

2) The Central Coupling Field

The central coupling field provides the capability to consolidate all external connections to and from the computer in a single field. This is very advantageous for “online” or parallel operation of the computer; a total of 20 coupling cables for 20 connections each can be accommodated. The connections are coaxial, ensuring good shielding throughout.

3) 10/100 V Adaption Unit

The adaption unit consists of 20 differential amplifiers with individual zero adjustment and individual power supply. The inputs and outputs of the adaption amplifiers are accessible via shielded connecting cables at the coupling field of the main computer’s problem board.

Additional analog and logic computing components in groups of up to 20 each can find accommodation in the expansion system. For the analog components, selection system, mode control, and overload indication are provided; for the logic section, clock and control signals are taken from the main computer. In this way, the computing capacity of the EAI-680 can be greatly extended with additional computing components.

V. Automatic Input/Output System (680 I/O Teletype Station) — New

The new EAI-680 input/output system gives the programmer the ability to automatically input and output data and commands. The operator console contains a standard Teletype ASR 35 unit — typewriter, paper tape reader and punch — plus power supply and the necessary coupling devices for connection to the EAI-680.

The I/O system can be used in each of the following operating modes:

  • Local: The teletype unit can be used as a normal typewriter or for preparing paper tapes. In this mode it does not interact with the EAI-680.
  • Attenuator Set: By entering the potentiometer address and desired value on the typewriter, a potentiometer can be set.
  • Reprogram Sequential: The setting of all potentiometers is punched onto paper tape. This tape serves as a stored program for a given problem configuration, allowing later repetition of the potentiometer settings.
  • Readout Sequential: All amplifiers (A), potentiometers (P), integrators in test mode (D), connecting lines (T), and variable function generators (F) can be read out and printed in any order.
  • Reprogram: A paper tape with the stored address and potentiometer value is read in and the potentiometers are set.
  • Readout: Any component selectable at the 680 operator panel can be addressed and read out via the teletype typewriter.

VI. Digitally Controllable Function Generators — New

To reduce computation time and increase data throughput — as demanded of modern high-speed hybrid computers — EAI has developed digitally controlled function generators (DCFG) as an extension to the Analog/Hybrid computer EAI-680. In a hybrid system, these can be completely set by the digital computer, while the necessary storage locations for function storage are present in the DCFG unit itself. Communication with the DCFG system can occur at a speed of microseconds and at the maximum output speed of the digital computer.

To perform this high-speed operation, the digital computer can create a table of X and Y coordinates and enter these into the memory of the DCFG unit, which is constructed from integrated circuits. If no digital computer is available, the DCFG can be programmed via a teletype unit, e.g., ASR 33 or KSR 35.

Key specifications:

  • Fully transistorized
  • Input voltage: ±10 V
  • Output voltage: ±10 V
  • Number of X and Y values: 16 to 24 bits, of which 9 bits for X and 14 bits for Y
  • Resolution in X direction: 50 mV
  • Resolution in Y direction: 2 mV
  • Maximum slope: 400 V/V
  • All 16 values can be read in in less than 60 µs

3 DCFGs are housed in a 19-inch chassis, so they can be inserted into any 19-inch rack, the 680 Expansion System, or the Resolver Expansion Area. Up to 9 DCFGs can be installed in the 680 console. The units have their own power supply, buffer memory, and addressing system.

Compared to conventional variable function generators, the DCFGs have significant advantages: entering and storing a function in microseconds, storage of 16 words of 24 bits, continuous linear interpolation of the function, and changing all 16 values in less than 60 µs.

Important Notice: EAI Devices from British Manufacturing

Are research funds from the currency offset agreement between Great Britain and the Federal Republic of Germany available to you? Or can you submit a corresponding application? If so, it will be of interest to learn that EAI is in a position to offer all standard EAI computing systems and accessories from British manufacture through its sister company EAL (Electronic Associates Ltd., Burgess Hill, England).

EAL 610 — Hybrid System Installation at City University London

April 30, 1968 marked the official commissioning of the 610 computing system at the City University of London. Pictured at the ceremony are (from the left): Prof. M.A. Jaswon, Head of the Department of Mathematics, the City University; Mr. Chris R. Peter, General Manager of EAL Ltd; Dr. J. S. Tart (partially hidden), Vice Chancellor, the City University; Rt. Hon. Lord Penney, Rector of Imperial College of Science and Technology; Sir Michael Turner, Deputy Pro-Chancellor, the City University; Mr. Henry N. Lewis, Sales Manager of EAL Ltd; and Dr. V. L. Price, Professor of Computer Science, the City University.

EAI Series 430 DataPlotter — A New Dynamic Concept in Digital Plotting

Specifications:

  • Usable Plotting Surface: 30” × 30”
  • Resolution: 0.002”
  • Slew Speed: 30”/second
  • Line Drawing: up to 20”/second depending on length of line
  • Free Run Drawing: up to 20”/second depending on data point spacing
  • Curve Mode Drawing: up to 16”/second depending on curvature
  • Point Plotting: ¼” spacing between points — 810 points/minute
  • Symbol Printing: ½” spacing characters — 770 to 350 characters/minute
  • Paper Handling: Vacuum system holds paper ranging from 8½” × 11” to 30” × 30”
  • Color: EAI Blue with white and satin chrome plate trim

The EAI Hybrid DataPlotter, Series 430, will be covered in detail in the next EAI-Report, issue 015!

The Series 430 DataPlotter offers significantly higher writing speeds than comparably priced incremental plotters with step motors, especially in curve mode and for sharp curves.

EAI Accessories — Measuring Lead Holders

Various measuring lead holder stands are available as accessories, including floor-standing (H2T, H3T) and table-standing (H2B, H3B) versions with rotatable holder arms for organizing patch cables and test leads. Prices range from DM 165 to DM 245.

EAI University Support Program 1968 — VAT Exemption

Educational institutions — technical universities, state engineering schools, etc. — purchasing an EAI fully transistorized desktop analog computer TR-20 or EAI Analog/Hybrid computer PACE 8/SA receive a system and educational discount (Educational Discount) of up to 20% off the duty-free list price. The discount level depends on the computer type and order scope. Customers ordering systems or devices with a customs exemption application can be supplied free of import duty and VAT.

EAI Class B Devices and Systems

EAI is currently in a position to offer the following EAI-PACE devices as “Class B” systems (used for a period in one of EAI’s computing centers in the USA and Europe, offered at substantially reduced prices with normal warranty and delivery conditions):

  • 1 EAI-PACE analog computer E-40, type TR-48/SE
  • 1 EAI-PACE desktop analog computer, type TR-20
  • 11 DATAPLOTTERS, model 3110
  • 1 VARIPLOTTER X-Y recorder, type 1110
  • 1 DIGITAL COMPUTER PDS-1020 (extremely cost-effective)

EAI Series 6200 Versatile Flight Instruments — Digital Measuring System

The Series 6200 Digital Measuring System consists of a basic chassis containing the power supply, 4-digit NIXIE readout, and silicon solid-state circuitry, plus provisions for up to two plug-in modules. For measurement of DC and AC voltages, frequency, period, time interval, and other electrical parameters, the Series 6200 provides the display; the plug-in module determines the application. This plug-in approach permits buying only those measuring capabilities currently required and provides unparalleled versatility in the low-cost digital measuring field.

Trade Fairs 1968

  • Deutsche Luftfahrtschau 1968 — Hannover Airport, 26 April–5 May: EAI participated with great success.
  • INTERKAMA 1968 — Düsseldorf, 4th International Congress with Exhibition for Measurement Technology and Automation, 9–15 October 1968. EAI exhibits in Hall B, Stand 2146.
  • Electronica 68 — Munich, 7–13 November 1968. EAI exhibits in Hall 15, Stand 15003.

Brush Mark Series Strip Chart Recorders

Various portable Brush Mark series strip chart recorders are available as accessories through EAI:

  • Mark 260: 6-channel portable, low cost-per-channel, pressure-fluid rectilinear writing in 2 colors, 4 event markers standard, built-in preamps, 1 mV sensitivity, only 65 lbs.
  • Mark 220: New high-performance portable, weighs just 25 lbs, uses same patented writing system as Mark 200 Series.
  • Mark 280: Dual 80 mm position feedback pen motor recorder, portable dual-channel system with rectilinear forced-fluid writing, “double-width” 80 mm channels.
  • Mark 250: Fastest, most versatile strip-chart recorder. To 10 Hz full scale, 40 ms rise time. Contactless servo. Detachable chart magazine. Portable or rack mounting.
  • Mark 2300: Lightbeam oscillograph — applications almost unlimited. Simple incandescent light source is fail-safe.

EAI 640 Digital Computer — Installation at TU Berlin

In recent weeks, EAI installed a digital computer EAI-640 at the Chair and Institute for Electrical Machines at TU Berlin (Prof. Dr.-Ing. Nünberg). In addition to the central unit with 8,192 core memory locations, it includes a Teletype unit Model ASR 35, i.e., typewriter, paper tape reader and punch. The system is to be used for calculating the optimal control of main drives on hot-strip reversing mills.

EAI-640 key data:

  • Word length: 16 bits plus memory protection bit
  • Cycle time: 1.65 µs
  • Core memory capacity: expandable from 8K to 32K words
  • Hard-wired multiplication and division; hard-wired square root extraction available
  • Complete set of I/O media: paper tape, punched cards, magnetic tape, printer, disk
  • Extensive software particularly suited for scientific calculations

EAI Series 150 Processor — Special-Purpose Analog Data Processor

A special-purpose analog data processor assembled from plug-in components, with the following features:

  • System accuracy better than competitively priced alternatives
  • Completely self-contained
  • Interfaces with DC control, conditioning, and instrumentation systems
  • Easy to assemble, calibrate, and maintain
  • Modules are complete and ready for installation

EAI European Education and Training Programme

Programming, operating, and maintaining a computer — whether analog, digital, or hybrid — requires specialized training. EAI provides this training through introductory and advanced courses in computing and simulation. These courses cover all aspects from hardware maintenance to the most modern computing techniques; they are conducted regularly at EAI training centers and in cooperation with technical colleges and universities.

Courses available:

  • Analog Simulation and Computing: Provides basic knowledge in the application of the analog computer for computing and simulation.
  • Parallel Hybrid Programming: The concept of digital logic is explained; theoretical and practical training in programming and operating parallel hybrid computers.
  • Hybrid Simulation and Computing: An insight into the operation and programming techniques of hybrid simulations and hybrid computing is provided. The course is oriented toward the EAI-690 system.
  • 640 Programming Course: Participants become familiar with the hardware and software of the digital computer. After completing the course, participants are able to work successfully with the EAI 640.
  • 693 Programming Course: Covers first the hardware and functions of the interface system EAI-693, then operation and software.

Basic courses for all EAI devices and systems are also offered; these courses (typically 2–3 days) provide an insight into the operation, construction, and use of the machine.

AICA 1968 — International Symposium on Analogue and Hybrid Computation Applied to Nuclear Energy

The “Association Internationale pour le Calcul Analogique” (AICA) is organizing an International Symposium on September 16, 17, and 18, 1968, in Versailles (France) on the use of analog and hybrid computers for solving problems in the field of nuclear energy. Applications from the chemical industry are also covered in various papers. Papers are given in either French or English, with simultaneous translation provided.

For further details, contact:

  • Symposium International sur le Calcul Analogique et Hybride Appliqué à l’Énergie Nucléaire, DEG/SER, CEN-SACLAY, 91-GIF-sur-YVETTE, France
  • EAI Electronic Associates GmbH, Bergdriesch 37, 51 Aachen, Germany

EAI 8900 Hybrid Computing System for Great Britain

The EAI 8900 hybrid system — combining the EAI 8400 Mod II digital computer with the EAI 8800 analog computer — provides a fully integrated hybrid computing system. The EAI 8400 Mod II digital computer combines logical decision-making, high computation speed, accuracy, and extended memory characteristics with the parallel operation, high speed, power, and flexibility of the EAI 8800 analog computer.

EAI is pleased to announce that its manufacturing partner EAL (Electronic Associates Ltd.) in England has received the order for a hybrid computing system EAI 8900; the customer is the Central Electricity Generating Board (CEGB) in London.

The hybrid system will be built at the EAI parent plant in the USA. The digital section is the EAI 8400 system with a core memory capacity of 32,000 words, complemented by extremely powerful digital and hybrid software. The coupling system EAI 8930 connects to three Analog/Hybrid computers EAI 8800. These have a computing capacity of 630 amplifiers; the variable function generators can be set via punch cards; a large number of nonlinear elements is included. A corresponding number of X-Y switches, multi-channel recorders, large-screen displays, etc. complete the system.

Many problems in science and technology — especially those dealing with the dynamic behavior of complex systems — are very difficult to solve either by analog or digital methods alone. This naturally leads to coupling both methods to obtain faster, better, and more cost-effective solutions. Hybrid computing systems are ideal for problems of this type, e.g., control and monitoring of power plants under varying load. CEGB uses the hybrid system EAI 8900 as an important instrument for the development and control of nuclear power plants.

The EAI 8900 at CEGB will be the largest hybrid system outside the USA. Experts claim that its capabilities for technical-scientific calculations are unique in Great Britain and perhaps in all of Europe.

New “Fiber-Tip” Writing System for EAI X-Y Recorders VARIPLOTTER

This new writing system is available as an accessory to EAI X-Y recorders “VARIPLOTTER” in the colors black, brown, red, and blue. The new writing system draws clear, sharp lines that do not smear at slow writing speed and do not break at full speed. It also permits quick color changes. The EAI Variplotter gives a 20% throughput gain.

EAI PDS 1020 Digital Computer

The PDS engineering interpreter transforms the PDS general-purpose digital computer into a powerful, easy-to-use engineering and scientific computer. Features include fixed-point and floating-point I/O, 8 significant figures, multiple loop counters, over 20 arithmetic/control/modification/decision instructions, immediate typewritten records of all retained programs, immediate punched tape record of all retained programs, up to 15 retained programs at any time (all variable length), and all retained programs may be linked for more powerful problem solving.

The interpreter can also transform the PDS 1020 into a digital incremental plotter under user control, with support for over 40 plotting symbols, scaling and offset by internal interpreter routines.

EAI Electronic Associates GmbH, 51 Aachen, Bergdriesch 37. Tel. (0241) 26042. Telex: EAI-D-842625. Copyright EAI 1968.