Mainframes were too expensive to be used by one person. They were equipped with some quantity of terminal units, sometimes known as monitors to allow many users to work with one machine.
First computers used teletypes as input/output devices. They quickly evolved to printing serial terminals - electronic printers with keyboards. Finally, display terminals with CRT tubes gained popularity. Later, many CP/M machines used only text mode, so it was just cheaper to use serial port terminal instead of designing a whole display circuitry from scratch. Terminals became more and more sophisticated, many units were little computers with Z80 or 8080 microprocessors. Polish industrial model made by Mera Elzab had shift reporting capability from data monitored on it. It was quite complex device with its own software.
In late 80s, many offices decided to use terminals with modern PC technology. A high-end PC server with 386 or 486 processor had multi-user operating system and special serial port cards with 4, 8 or 16 ports (you can see them in this site too). Terminals were connected to this PC.
These terminals are still in use today (2012) with Linux and Unix technology. I've seen working serial terminal network in Cracow's City Transport in one of end tram stations (?Krowodrza Górka?) where it supported ticket selling/accounting coordination reliably.
Some smart terminals had pre-programmed form field editing capability, making this thing procesed independently of database systems. These terminals usually had buttons for programming which part of the form is field and how/when to switch between them. The only thing sent to mainframe was the data and the only thing received was form number and data to be displayed.

Click the picture above to get more information about the first Polish terminal - IMM Alfa 10

Some more photos of old terminals:
 - Early Regnecentralen printing terminal
 - Early Polish printing terminal (Mera)
 - Early Regnecentralen active terminal system
 - Printing terminal with magnetic reel recorder
 - Terminal with more modern magnetic tape recorder
 - Uknonwn terminal unit
 - Mera units in Elwro assembly plant
And more modern ones:
-K&K Lidia system (PC+4term) - 1987
-Budavox Hungarian terminals - 1987
-Polish Mera 7915OM (1987) (Src:IKS1987)
-Terminals used in 1986 in ZUS Warsaw
-Terminals used in 1986 in PLL LOT
-Mazovia talking to 2 terminals - 1986
-Mera 79321 (source unknown)

Unknown terminal (source: AV, 1984)

 (Sources of pictures above : "1000 słów o komputerach i Informatyce" and "Komputer" magazine)

Click a unit to get information, photos and tips...

Manufacturer Model Origin Display Year
Facit Terminal 4440 30M-F1 Sweden Monochrome white CRT 1986
Mera-Elzab EC-7915 Poland Monochrome amber CRT 1986
Mera-Elzab 79152 PC Poland Monochrome green CRT 1987
Ampex 210 Plus USA Monochrome amber CRT 1989
Wyse WY-120 USA Monochrome white CRT 1993
ITT Courier 9216 USA Color CRT 1986
Ericsson 9161 Sweden Monochrome CRT 1983
Siemens Bitel T3210 W.Germany Internal Mono CRT 1986
Siemens Multitel Fe Ap 90-1.1 W.Germany Internal Mono CRT 1989
Loewe MultiCom 715L W.Germany Color CRT 1988
Siemens MultiKom S1 W.Germany Grayscale CRT 1990
Loewe Multitel D W.Germany Grayscale CRT 1992
Televerket/Loewe Teleguide Sweden/W.Germany Grayscale CRT 1992
Unimor ANG-3001 (see Bosman 8) Poland External mono green CRT 1989
Mera-Elzab ??? (Prototype?) Poland Probably monochrome CRT 198?
Mera-Elzab VDM 79322 (CM 7233) Poland External Mono CRT 1992
Mera-Elzab 7951 OM Poland Internal Green CRT 1987
Alcatel Terminatel 258 France Internal mono CRT 1992
Philips Minitel 2 NMS 6202 France Internal mono CRT 1993
Magis/Alcatel Magis Club Rev. 2 France Internal mono CRT 1999
IBM IBM 3180 (incomplete) USA Green CRT 1986
Reuters SK 101 BL USA? ?? 1988
Humantechnik Textel Compact Germany LCD 1993
Creator / Fura Elektronik IKT-5a Poland RGB Monitor 1993
Fura Elektronik IKT-6 Poland VGA Monitor 1998
Ultratec Minicom 6000 USA Built-in VFD 2000
Compaq Clipper IA-1 USA Built-in LCD 2000


Peripherals and accessories (including PC expansion cards terminals):

Name Type Terminal
Accodata Serial switch Serial printer switch All with serial port o/p
Serial splitter and multiport card multi-serial port All with serial port, computer with EISA.
Specialix IO-4 card multi-serial port All with serial port, computer with 16-bit ISA
4-port 8-bit ISA Serial card multi-serial port All with serial port, computer with 8-bit ISA
Olivetti multi-io card? ?multi-serial card? All with serial port, computer with 16-bit ISA
Specialix SI-Host Serial card multi-serial card All with serial port, computer with 16-bit ISA
Specialix SI-XIO Serial card multi-serial card All with serial port, computer with 16-bit ISA
Siemens Nixdorf SCB 1.0 Multi-serial +ISDN All with serial port, computer with 16-bit ISA