© Mark Ollig
In 1977, Dale Heatherington and Dennis Hayes developed the 80-103A, also known as the DC Hayes 80-103A data communications adapter. This full-duplex modem could transmit and receive data simultaneously at speeds up to 300 baud.
The 80-103A was used with the S-100 bus structure, which Micro Instrumentation and Telemetry Systems (MITS) originally developed for the Altair 8800 computer.
The S-100 bus was designed to be a 100-pin expansion bus that allowed users to plug in different peripheral cards and to expand or modify the computer’s capabilities.
With a common bus architecture among various computing machines, several companies began providing plug-in CPUs, memory, video, disk controllers, and other compatible peripheral cards for S-100-based systems.
The S-100 bus became the basis of the first personal computer hardware standard and often used Zilog Z80 CPUs and Digital Research’s 1974 Control Program/Monitor (CP/M) operating system.
The name “S-100” was derived from its 100-pin edge connector. The “S” in S-100 stands for “system.”
The 80-103A enabled data transfer within the S-100 bus architecture when connecting computers, printers, and data terminals.
It allowed computing devices to communicate with other devices through the telephone network via a 24-volt DC-powered device known as a Data Access Arrangement (DAA), usually provided by the local telephone company.
Western Electric had manufactured the DAA wired to a business’s computing equipment, allowing data transmission over telephone network lines connected to various computing equipment.
The 80-103A supported numerous computers, printers, and data terminals. It was sold by retailers in the United States and Canada, as well as through Hayes Microcomputer Products.
The price of the 80-103A in 1978 was $595.
A 1979 advertisement from Byte magazine sold it for $499, and a 1980 advertisement from Popular Electronics magazine listed it at $395.
The 80-103A was used with other S-100 bus-compatible communications boards installed in computers during the 1970s, including:
• Altair 8800,
• IMSAI 8080,
• Sol-20,
• Cromemco Z-2,
• North Star Horizon.
Much of the storage for these computers consisted of paper or audio cassette tapes, eight-inch “memory,” or 5.25-inch floppy diskettes.
These hobbyist computers from that era usually had less than 64KB of dynamic random-access memory (DRAM) stored on computing chips.
Many did not have a video display screen and used LED lamps to indicate status and computed results; the user input data into the computer using front panel switches or tape.
Back then, computers required the user to understand the hardware and programming thoroughly to use them effectively.
Despite a steep learning curve, those 1970s computers became popular among electronic hobbyists and computer enthusiasts.
The S-100 bus became a de facto standard and was later adopted as the Institute of Electrical and Electronics Engineers (IEEE-696) computer bus standard.
However, in 1981, the S-100 bus was replaced by other architectures, such as the IBM PC Industry Standard Architecture (ISA) buses.
In 1981, the 80-103A was superseded by the DC Hayes Smartmodem 300.
The Smartmodem 300, a faster and more reliable 300-baud modem, also included what became the industry standard AT command set for modem control.
This set of commands is composed of short text strings that can be combined to create instructions for tasks like dialing, hanging up, and modifying connection settings.
Most dial-up modems utilized the Hayes AT command set. Some command examples include:
• AT – Attention. Used to start all AT commands.
• ATD – Dial the phone number.
• ATH – Hang up the phone.
• ATS – Set the modem’s speed and other parameters.
• ATA – Get the modem’s status.
• ATZ – Reset the modem to its factory default settings.
Using the Hayes command set, one modem would need to dial the phone number of the other modem via an old-fashioned POTS (Plain Old Telephone Service) telephone line to establish a data connection.
Let’s use 123-456-7890 as the receiving modem’s phone number and connect our modem with it using the Hayes command: ATD1234567890.
And always, make sure you hear the dialtone before placing your call.
The Hayes command set, named after Dennis Hayes, the founder of Hayes Microcomputer Products, profoundly impacted the history of online computing, as folks connected their computers directly with other computers and online dial-up services, including CompuServe, Prodigy, AOL, and Hobbyist Bulletin Board Systems (BBS).
I still have a vintage 1978 DC. Hayes 80-103A printed wiring card and user guide.
The 45-year-old user guide introduction begins with “The time has come for microcomputer users to expand the power of their systems through the use of the existing telecommunication networks which are capable of connecting their computers to remote devices such as terminals, other small computers, or timesharing systems.”
Little did we know in 1978 where the technology would take us in 2023.
