DataArt Museum. Video Terminal ADM-3A. The car is heavy, reliable, killer

One of our favorite exhibits is a classic example of an American design school, a reliable and inexpensive device that instantly conquered America in the mid-1970s. Together with the inspiration of the DataArt museum, Gleb Nitsman recalled the evolution of input-output devices and carefully considered the ADM-3A terminal for interaction with the PDP-series computer.

The very first computers required direct contact and deep knowledge of the internal structure from a person. The one who wrote the program had to also switch the required toggle switches. The next stage in the evolution of interaction began with the advent of punched cards and punched tapes for data entry and alphanumeric printers for outputting results. Soon, electromechanical typewriters (say, in the 1970s in the USSR, this was the Czech Consul-256) or teletypes began to be used as an input device.
')
The terminals on the basis of cathode-ray tubes for the first time, in all likelihood, were used by the US military in the SAGE project. In the civilian car market, DEC became the pioneer; in 1961, it supplied its PDP-1 with a display in an elegant hexagon case.



The 1970s, when the timesharing technology allowed connecting several I / O devices to a single computing resource, began the heyday of video terminals. Lear Siegler introduced its development, the ADM-3, in 1975. The shape of the candy bar resembled a sink. According to Dennis Kagan, who worked as a regional sales manager at LSI since 1973, the name of the ADM series was deciphered as American Dream Machine - the American Dream Machine. With very similar characteristics, the ADM-3 video terminal cost almost $ 1,500 cheaper than the development from DEC of the same time .

The functional scheme of the device is as follows:



All the electronics of the device was placed on a single printed circuit board, and was implemented exclusively on the IC (integrated circuits) of small and medium degree of integration without the use of microprocessors (which then already existed).



The soldering of the component leads was made by a wave . This allowed LSI to sell ADM-3 at a record low price for its time - $ 995.

The advertising slogan in the Computerworld newspaper dated July 30, 1975 introduced a new concept, dividing the terminals into simple (dumb) and smart terminals (smart, which were attached to intellectual ones that had even more functions). The first, in particular, ADM-3, did not allow to manipulate the data already entered, but they were much cheaper. A detailed description of the terminal ADM-3 can be found here .



Later, the company began selling sets for self-assembly of terminals , which included the necessary electronic components and detailed instructions for assembly and configuration. Subscribers automatically become members of the Dumb Terminal Fan Club .



The DataArt collection features the next version of the device, the ADM-3A, which allows you to move the cursor around the screen using CTRL sequences and supports both character registers when displayed on the screen. However, in our instance, only 12 of the 14 cases of the buffer memory of the screen and one of the two ROMs of the character generator are installed, so the lower case characters are displayed as upper (as in the ADM-3). Apparently, installing additional memory housings and a second ROM would allow the use of lowercase letters.



The device is a 12-inch monochrome display capable of displaying 1920 characters: 80 each in 24 lines. The display shows US-ASCII characters, each of which is formed by a 5 by 7 dot matrix. The brightness of the image can be adjusted.


The keyboard consists of 59 keys: 47 alphanumeric characters and 12 control keys


Important components of the terminal circuitry on the board: 1. RS232 port transceiver; 2. ROM character generator; 3. shell buffer memory screen


DIP switches allow you to flexibly configure the terminal, choosing the exchange method (RS-232 or current loop), word length, number of stop bits, parity, half- or full-duplex operation, as well as the exchange rate from the standard series (75–19200 bits / with)


On the back of the terminal there are ports: one interface for communication with the host, and a serial expansion interface

Our copy was used as a system console to the PDP-11/34 minicomputer (it is also located in the DataArt museum) and belonged to a former hacker, who became an information security specialist, Alexei Smirnov aka ArkanoiD .

Andrei Smirnov explained: “PDP-11/34 by the time I got it was already a purely hobby subject. And the ADM-3a was not a workhorse, it is a very specific thing. The workhorse was the Rainbow 100+. ”


ADM-3 on the cover of Microcomputing Magazine (in the background). June 1979