Dornier DO 80 Analog Computer — Operator Manual

This document is an English translation of the original German-language operator manual for the Dornier DO 80 analog computer.

General Description
Computer Construction
Description of Operating and Display Elements
Construction of Computing Elements
- 4.1 Integrator Module
- 4.2 Summing Amplifier Module
- 4.3 Multiplier Module
- 4.4 Potentiometer Module
Programming Examples
Specifications

1. General Description

The DORNIER 80 is a universally compact 10-volt desktop analog computer. Its low weight and small dimensions (19-inch standard rack housing) make it a portable desktop computer. The computer can be stacked with other 19-inch equipment.

The layout of the programming field corresponds to that of larger computers, and the possibilities for patching the computing elements are similarly flexible. The DORNIER 80 differs from the usual educational computers in that it enables more advanced training and transition to large-scale computers.

For cost reasons, a replaceable programming field was omitted. Such a feature is, in any case, not common for computers of this price range.

2. Computer Construction

Above the programming field are the four potentiometer modules. Each module contains the associated patch-panel segment. On the right side is the control module with the display and operating panel, which for maintenance and repair purposes can be operated outside the computer via an adapter cable.

On the rear of the computer, in addition to the mains connection, are connectors for parallel operation of two computers as well as sockets for control signals (e.g., for connection and control of recording devices). The internal supply voltages are also brought out here.

3. Description of Operating and Display Elements

The individual operating and display elements have the following functions (see adjacent images):

Trim potentiometer for +10 V reference voltage
Trim potentiometer for −10 V reference voltage
Lamp panel for indicating the state of the up to four comparators
Overload indicator panel — per module there is one lamp indicating overload of the amplifiers in that module. Simultaneously, failure of both reference voltages is displayed.
Analog voltmeter with three switchable measurement ranges
“Overload Hold” switch — when this switch is activated, an overload automatically triggers the HT (Hold) operating mode.
Input sockets for the analog voltmeter
12-position selector switch for the analog voltmeter. With this switch, the following can be measured:
- Supply voltages: +Ref, −Ref, +15 V, −15 V, +12 V, +5 V
- Voltages applied at the green socket (7) versus ground, with the following measurement ranges:
  - ±1: ±5 V full scale
  - ±10: ±1.5 V full scale (note: labeled for 10 V machines)
  - ABGL: approx. ±150 mV full scale
- The differential voltage at sockets (7) in the DIFF position: approx. ±150 mV full scale
Mains switch with indicator lamp
Adjustment potentiometer for compute time in operating modes RR (Repetitive Computation) and 1× (Single-shot Computation). The product of the potentiometer setting and the setting of switch 11 gives the compute time — i.e., the time during which the computer is in the Compute state during “Repetitive Computation.”
Coarse selector switch for compute time. Using adjustment potentiometer 10 and switch 11, the compute time can be varied according to the following table:

Switch 11 position Pause time tp Compute time
0.1 0.1 0.1 to 1 sec
1 0.1 1 to 11 sec
1 1 1 to 11 sec
10 1 10 to 110 sec
Adjustment potentiometer for pause time. The pause time tp given at item 11 applies when potentiometer 12 is at the counterclockwise stop. From this value, it can be increased via the multi-turn potentiometer. Pause and compute times are reduced to one-tenth of the set values via key 21. Especially during operation with complementary integrators, an adjustable pause time can be useful, which is achieved via this potentiometer.
REMOTE control switch. This switch connects the DORNIER 80 as a slave computer to another DORNIER computer (“Master-Slave” operation). The timer of the slave computer remains separately functional and can be controlled as usual via keys 15 through 21. This provides an additional independent clock generator.
REMOTE control indicator. When the DORNIER 80 is switched as a slave computer, this lamp lights up.
IC key (Initial Condition). Pressing this key puts the computer in the IC (Initial Condition) operating mode, in which all normally patched integrators establish their initial conditions.

The bus bars DR and HT at the lower part of an integrator module are switched via transistors to relay ground depending on the operating mode. The individual modules are decoupled by diodes.

In operating mode IC:
- DR: transistor blocking (relay ground / relay ground)
- HT: transistor conducting (relay ground / relay ground)
HT key (Hold). This key activates the HT (Hold) operating mode, in which all integrators hold the computation while retaining their momentary output voltages. From operating mode HT, computation can be resumed by pressing the DR key (17).
- DR: transistor conducting (relay ground)
- HT: transistor conducting
DR key (Compute). This activates the Compute state and thus starts a computation. Further progression depends on which operating mode was pre-selected via keys 18 and 19. If neither the 1× key nor the RR key is pressed, the computer enters continuous computation mode. In this mode, the timer generates a ramp rising from −10 V to +10 V over the compute time, with the pause and compute times set at 10, 11, and 12, repeating — available at the rear of the computer for external time deflection of recording devices.
- DR: transistor conducting (relay ground)
- (Compute): transistor blocking (relay ground)
1× Compute key. After pressing the 1× key and then pressing the DR key (17), the computer remains in the Compute state for the duration set by potentiometer 10 and switch 11. It then returns to operating mode IC. Here too the timer generates a single ramp rising from −10 V to +10 V during the compute time, then returning linearly to −10 V during the pause time.
RR key. This key pre-selects the “Repetitive Computation” operating mode. After pressing DR (key 17), the Compute and Initial Condition states are cyclically traversed with the pause and compute times set at 10, 11, and 12. These times can be shortened to one-tenth of the set values via key 21. The timer always generates a repeating ramp rising from −10 V to +10 V during each compute period. The RR operating mode is exited after pressing the IC key.
mHT key (with HALT). After pressing this key, at the end of a computation cycle (in both RR and 1× modes), instead of returning to IC mode, HT mode is activated. The following difference applies:

In RR “with HALT” and DR “with HALT,” the timer output (ramp) is also held at +10 V, which is useful for the X-axis of an XY recorder. In 1× “with HALT,” the computation is held with instantaneous values retained, but the ramp returns to −10 V. By pressing the DR key again, the computation can be resumed by a defined interval. This enables step-by-step computation.
T/10 key. This key accelerates the entire computation process by a factor of 10, independently of the time constants selected on the programming field for individual integrators. Simultaneously, the timer is accelerated tenfold.
Function switches. These keys are provided as freely available function switches on the programming field. They each deliver a logical output signal with TTL level at the programming field, which is hard-wired with a relay. Only when the additionally available relay driver input on the programming field is supplied from another source do the keys deliver only their logical output without affecting the relay. If several switches are to be actuated simultaneously, it is possible to press and hold one of them, briefly press the others, then release the first. Closing the normally closed contact of the key also changes the other switch states.

Switch 11 position	Pause time tp	Compute time
0.1	0.1	0.1 to 1 sec
1	0.1	1 to 11 sec
1	1	1 to 11 sec
10	1	10 to 110 sec

Rear Panel Connections

On the rear of the device the following connections are present:

Socket panel (item 23):

HT, DR — These outputs are identical to the correspondingly labeled sockets on the front programming field.
HTZ, DRZ — Control signals of the timer. In operating modes 1× Compute and Repetitive Computation, these are identical to the HT/DR signals. In continuous computation mode, the timer operates repetitively with the set values to provide a time deflection for external devices in that mode as well.
KRZ — In addition to HTZ and DRZ signals, KRZ serves to indicate the timer state. The output transistor is conducting as long as the timer is in its return phase.
HTZ, DRZ, KRZ relay contacts / TAB, THT, TDR — These signals each drive a relay to provide potential-free signals (e.g., for pen control on XY recorders).
TAB, THT, TDR inputs — These inputs are parallel to the IC, HT, DR keys. By applying a ground potential, the corresponding functions can be triggered as if the key were pressed. This enables simple remote control of the computer.
RAMP — At this socket, the analog output signal of the timer is available.

Control diagram: [Describes timing states: Compute → Hold → Initial Condition → Hold → Compute, with timer ramp transitions shown]

External lines A, B, C, D — At these sockets, the external lines labeled A, B, C, D in the potentiometer modules are brought out. These lines are also available at connector 25.

Ground sockets — Three signal-ground sockets and two relay-ground sockets are present.

Remote control connector for connecting additional DORNIER computers — The computer generates separate signals for parallel switching of additional computers. These control the switching of operating modes as well as overload hold. Signals are TTL-level in positive logic. Up to 6 computers can be coupled by simply connecting the sockets 24.
External wiring to the programming field — External recording devices (XY plotters, oscilloscopes) can be connected via this connector. The time deflection is then connected with an external line on the rear socket panel (23). This provides the connection to the external device via an external connector. This connector can also be connected to the corresponding connector of a second computer in parallel operation.
Mains fuse
Mains connector
Test sockets for internal power supplies

4. Construction of Computing Elements

Each computing element consists of a printed circuit board for mounting the components and the patch-panel segment permanently connected to it.

Due to the identical wiring of all 16 positions for computing elements, each element can be inserted in any desired position.

Currently available modules are:

One module with one integrator
One module with three summing amplifiers
One module with two complete multipliers and two additional summing amplifiers

4.1 Integrator Module

The patch-panel segments of the three module types are shown in the diagram [with labels X, J, H/HT/DR for integrator; summing amplifier; and multiplier].

Each integrator is separately controllable in its operating modes and time constants. Only via key T/10 is a general acceleration of all integrators by a factor of 10 applied.

Integrator circuit: The diagram shows a standard op-amp integrator circuit with capacitors selectable for different time constants, operating mode control via HT/DR/AB bus lines, and a 1/10 speed switch.

If the HT and H sockets of an integrator’s control field are connected, and S and DR are connected, the operating mode control of this integrator is governed by the IC, HT, and DR keys. Bridging the sockets labeled E configures the integrator as a summing amplifier.

4.2 Summing Amplifier Module

Each summing amplifier module contains three summing amplifiers:

The upper summing amplifier operates with fixed feedback and two inputs of unity gain (×1).
The middle summing amplifier has one unity input and two ten-times inputs (×10), plus an available summing junction and fixed feedback.
The lower summing amplifier requires an externally programmed feedback and can therefore also be equipped with inputs of 0.1 gain.

4.3 Multiplier Module

A multiplier module contains two complete multipliers plus two summing amplifiers. The multipliers require patching of the Z-input such that for multiplication Z is connected to the output, and for division the output is connected to the Y-input instead.

4.4 Potentiometer Module

The patch-panel segment belonging to a potentiometer module includes the following sockets:

T1, T2 — External connection lines to the rear of the computer
E1, E2 — Comparator inputs
K — Logic comparator output (TTL level)
RTR — Relay driver inputs
HAND — Logic output of a function switch
+Ref, −Ref — Reference voltages
SP, A — Limiter connections
P1, P2, P3 — Grounded potentiometers
P4 — Ungrounded (floating) potentiometer
Black — Ground

The upper relay is directly coupled to the comparator, but can be switched via the RTR input with priority by another TTL signal. The same applies to the lower relay and the hand switch. The limiter has its own trim potentiometers (accessible at the patch field) and is connected to the summing junction or output of the amplifier to be limited via SP or A respectively.

5. Programming Examples

Several simple computing circuits with corresponding patch-panel wiring are shown:

Example 1: y = −x₀ − ∫(x₁ + x₂ + 10·x₃)

Example 2: y = −x₀ − 10·∫(x₁ + x₂ + 10·x₃)

Example 3: y = −(x₁ + x₂ + 10·x₃), for H = open; y = 0 for H connected to ground

Example 4 (Three summing amplifiers):

Y₁ = −(X₁ + X₂)
Y₂ = −(X₃ + 10·X₄)
Y₃ = −(X₅ + 10·X₆)

Example 5:

Y₁ = −1/10·(… )
Y₂ = −5·(X₂ + X₃)
Y₃ = −(0.1·X₄ + 5·X₅ + 0.1·X₆)

Example 6 (Multiplication/Summation):

Y₁ = X₁ · X₂
Y₂ = −(X₃ + X₄)

Additional examples show integrator-based circuits including second-order differential equation setups.

6. Specifications

1. Basic Unit

Parameter	Value
Dimensions (D × H × W)	280 mm × 235 mm × 445 mm
Reference voltage accuracy	±0.25%
Temperature coefficient	0.04%/°C
IC (Initial Condition) time	10 ms to 100 sec
Compute time	10 ms to 110 sec

2. Amplifiers

Parameter	Value
Gain resistor accuracy	0.25%
Max. output current at 10 V	5 mA
Short-circuit and reverse-voltage proof	Yes
Bandwidth (−3 dB) at 20 Vpp (100 kΩ / 100 kΩ)	> 20 kHz
Max. output voltage slew rate	—
Overload recovery time	< 1 ms

3. Integrators

Parameter	Value
Capacitors	1 μF, 0.1 μF, 0.01 μF
Capacitor accuracy	0.5% for 1 μF and 0.1 μF; 1% for 0.01 μF
Mode switching time (IC, DR, HT)	< 2 ms
Drift in HT (with 1 μF capacitor)	80 μV/s

4. Potentiometers

Parameter	Value
Type	10-turn wirewound with scale
Resistance	10 kΩ
Short-circuit and reverse-voltage proof	Yes

5. Comparators

Parameter	Value
Sensitivity	10 mV
Response time	< 1 ms

6. Multipliers

Parameter	Value
Static error	1% FS
Bandwidth at x = 10 V, y = 10 V sin	> 20 kHz
Max. output current at ±10 V	5 mA
Short-circuit and reverse-voltage proof	Yes