Northern Telecom Displayphone

Dublin Core


Northern Telecom Displayphone


hardware: displayphone


Historical context
By Z. Stachniak with input from D. Cuddy

In February 1981, telecommunications giant Northern Telecom announced the Displayphone – a landmark office automation product designed to integrate voice and data in a convenient, easy-to-use desktop unit. The January 1988 Datapro Research Corporation's report described the Displayphone as a device that:

   opened up the integrated voice/data terminal market [...] The first
   commercially available device of this kind, the Displayphone [...]
   attracted a great deal of attention in the computer industry, particularly
   among workstation vendors. Many vendors were interested in
   bringing their products to executive desks; thus the Displayphone
   was a factor in the emergence of a new class of equipment  –
   executive/professional workstation.

The Displayphone was developed by Bell-Northern Research in Ottawa and manufactured by Northern Telecom. Its first model–the NT6K00–was a small desktop terminal with a handset, speakerphone,  an integrated 300 bps modem, built-in 7-inch monochrome display, dial and screen pad, and five soft keys. A retractable QWERTY-style keyboard was stored within the unit's base. The device could operate with two independent phone lines for simultaneously handling voice and data calls which allowed users to talk on the phone while accessing and viewing information from remote dial-up data services. In addition, the unit could be used as a data terminal connected to a local computer via the RS 232C port. It could also access database services via an external modem and drive a printer through a parallel I/O interface.

The Displayphone featured a 90-number telephone directory, on-hook as well as automatic and hands-free dialing, last number redial, a recall work list and call hold. Other features available were a continuous day/date clock, a telephone call timer,  and a reminder service that brought messages to the user's attention. The user interace was designed for ease of use, with context-sensitive prompts displayed on the screen and soft keys that led the user from one operation to another.

Between 1981 and 1986, Northern Telecom released several models of and upgrades to the Displayphones, including the PLUS (released in 1984) and the 220 (offered in October 1986). Another variant, the SL-1 Displayphone, when designed to access the voice and data capabilities of Northern Telecom's popular SL-1 PBX.

By the mid-1980s, Northern Telecom had already faced competition from other vendors including AT&T, Davox, InteCom/Wang, and Rolm. Nevertheless, the Displayphone continued to have the largest installed bases of any of the competing products, which, according to the 1988 Datapro Research report, was at around 50,000 in 1987.

Following the success of the Displayphone in the enterprise market, NT proceeded to develop its successor–the Meridian M4020 Integrated Terminal–which was released in 1985. Instead of a pair of analog telephone interfaces, the M4029 connected to the network over an integrated 2.56Mbps digital interface.

Displayphone NT6K00 technical specifications
  • CPU: Intel 8085, 8-bit,
  • ROM: 40KB with Displayphone firmware,
  • keyboard: QWERTY, retractable, stored within the unit's base,
  • dial and screen pad: built-in, containing 12 dial keys, 5 softkeys, and 12 programmed keys,
  • display: 7in, 24 lines, 40 or 80 characters/line, with the 25th line used for labeling of softkeys,
  • voice ports: two analog PSTN phone lines, integrated Bell 103-type modem,
  • data ports: RS 232C (connection to a local computer or external, modem), parallel I/O port (for printer),
  • transmission rates: from 75 to 1200 baud for RS 232C and from 65 to 300 boud for dialup,
  • peripherals: Displayjet printer.
Museum's holdings
  • Displayphone NT6K00 AA (1982),
  • Displayphone NT1K00 AA, serial number 1271004601 (1982),
  • Displayphone NT6K90 AC, serial number 29E0004529 (1984),
  • Displayphone User Guide, Northern Telecom, June 1981,
  • Displayphone, The integrated voice and data telephone concept from Bell Canada, Bell Canada, 198?
  • Displayphone User Guide, Northern Telecom, February 1982,
  • Datapro Report C25-662-102 (Terminals), Datapro Research Corp., January 1988,
  • Displayphone User Guide, Northern Telecom, June 1981,
  • Displayphone User Guide, Northern Telecom, February 1982.


Northern Telecom


North America, 1980s.

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Northern Telecom, “Northern Telecom Displayphone,” York University Computer Museum Canada, accessed July 19, 2024,

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