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DECtalk DTC01 (with a cat for scale)
DeveloperDigital Equipment Corporation
Typespeech synthesizer, text-to-speech
Release date1984 (1984)[1][2]
Introductory priceDTC01 US$4,000 (equivalent to $11,731 in 2023)[3]
ConnectivityRS-232C serial interface[1]
PlatformOpenVMS, ULTRIX, Digital UNIX, Windows NT
Dimensions(DTC01 = W 45.7 cm x D 30.48 cm x H 10.16 cm ( 18in x 12in x 4in) )
Mass(DTC01 = 7.2 kg (16 lbs))
DECtalk demo recording using the Perfect Paul and Uppity Ursula voices

DECtalk[4] was a speech synthesizer and text-to-speech technology developed by Digital Equipment Corporation in 1983,[1] based largely on the work of Dennis Klatt at MIT, whose source-filter algorithm was variously known as KlattTalk or MITalk.[5][6]

Uses ranged from interacting with the public to allowing those with speech disabilities to verbalize, include giving a public speech.[7][8]


Announced December 1983, a trickle came February 1984; larger DECtalk quantities were delivered in March.[9]

They were standalone units that connected to any device with an asynchronous serial port. These units were also able to connect to the telephone system by having two telephone jacks. One connected to a phone line, the other to a telephone. The DECtalk units could recognize and generate any telephone touch tone. With that capability the units could be used to automate various telephone-related tasks by handling both incoming and outgoing calls. This included acting as an interface to an email system and the capability to function as an alerting system by utilizing the ability to place calls and interact via touch tones with the person answering the phone.

Later units were produced for PCs with ISA bus slots. In addition, various software implementations were produced, most notably the DECtalk Access32. Such implementations began as explorations into real-time software synthesis on general purpose CPUs,[10]: 2 subsequently delivering a DECtalk Software product for Digital Unix and for Windows NT on Alpha and Intel processors.[11] Certain versions of the synthesizer were prone to undesirable characteristics. For example, the alveolar stops were often assimilated as sounding more like dental stops. Also, versions such as Access32 would produce faint electronic beeps at the end of phrases.

In the final years, early/mid-2000,[12] the DECtalk IP was sold to Force Computers, Inc. In December 2001, the IP was sold[13] from Force Computers, Inc, to Fonix Speech, Inc. (now SpeechFX, Inc.), which offers DECtalk as a small-footprint TTS system and in a computer program form.[14]


The New York Times wrote: "like a scratchy recording of a person with a lisp" but added "usually understandable."[4]

DECtalk had a number of built-in voices which were identified by the following names: Perfect Paul (the default voice), Beautiful Betty, Huge Harry, Frail Frank, Kit the Kid, Rough Rita, Uppity Ursula, Doctor Dennis and Whispering Wendy. Each of the voices were editable by adjusting various parameters (such as throat size, crossover frequencies, etc.).

Daisy Bell sung by DECtalk

DECtalk understood phonetic spellings of words, allowing customized pronunciation of unusual words. These phonetic spellings could also include a pitch and duration notation which DECtalk would use when enunciating the phonetic components. This allowed DECtalk to sing.


  • The DECtalk engine was notably used in the US National Weather Service's first "Console Replacement System" (CRS) installations in the late 1990s for NOAA Weather Radio. As of 2003 it had all but been replaced by a far more modern engine called Speechify from SpeechWorks (not to be confused with the iOS app of the same name).[15] DECtalk's Perfect Paul preset voiced station identifications on many NWR stations until the CRS was replaced by a new system, called the "Broadcast Message Handler" (BMH), in 2016.[16]
  • Huge Harry is predominantly used in ATIS messages for most airports providing such information including prevailing weather conditions.
  • One of the early uses was a "text to voice" system that read an individual's emergency medical information (medications, allergies, doctor, insurance and contact info stored in a database) to hospitals telephoning in about patients presenting at emergency rooms. The company, Med-Fax, created by David Grober in 1986, used the DECtalk on an IBM platform, making it one of the early cross platform applications (DEC to IBM).
  • DECtalk can be used as part of a speech generating device for those unable to speak. A notable user was Stephen Hawking, who was unable to speak due to a combination of severe disabilities caused by ALS as well as an emergency tracheotomy.[17] Hawking used a version of the DECtalk voice synthesizer for several years[18] and came to be associated with the unique voice of the device. In 2011, Hawking's research assistant Sam Blackburn said Hawking still used a version of DECtalk identified on its board as the "Calltext 5010" manufactured in 1988 by SpeechPlus, Inc.,[19] because he identified with it and had not heard a voice he liked better. The CallText 5010 was still listed on Hawking's site as of 2015.[20] A team from Cambridge (UK) and Palo Alto eventually emulated the workings of the CallText 5010 on a Raspberry Pi, which Hawking used from January 2018 to his death in March of that year.[21]

In popular culture[edit]

  • The character "Dee Klatt" from Chipspeech was based on data from this device.[22]
  • In the sixth episode of Tales from the Darkside, Mookie and Pookie, the voice of Kevin "Mookie" Anderson is created with a DECtalk.
  • The video game Moonbase Alpha uses a software version of DECTalk for chat text. Several viral videos were created showcasing users using the chat in a nonsensical manner and using its ability to sing songs.
  • The experimental rock band The Space Negros uses DECTalk in their 1986 song "Robot."
  • DECTalk was used in the song "Music Non Stop" by the band Kraftwerk. (Released 1986) It was edited and recorded by Florian Schneider and Karl Bartos at Kling Klang Studio Düsseldorf.[23]
  • DECTalk's built in "Perfect Paul" voice has been ported to the freeware singing voice synthesizer UTAU by the user UtaUtaUtau.[24]


  1. ^ a b c DECtalk lets micros read messages over phone, By Peggy Zientara, InfoWorld, Jan 9-16, 1984, Page 21 and 23, ...DECtalk, which the company says will be available in March at a price of $4000...The DECtalk hardware, which fits easily under a 12-inch monitor...The unit attaches to a personal computer via an RS-232C serial interface...
  2. ^ Advertisement:We just turned every touch-tone phone into a financial clearinghouse., Computerworld, 18 Feb 1985, Page 39
  3. ^ Advertisement: INTRODUCING DECTALK THE REVOLUTIONARY NEW TERMINAL THAT LETS YOUR COMPUTER SPEAK FOR ITSELF., Computerworld, 23 Jul 1984, Page 70-71, ...The DECtalk system is available now for $4000* or less depending on quantity...
  4. ^ a b Andrew Pollack (January 5, 1984). "Technology; Audiotex: Data By Telephone". The New York Times.
  5. ^ Klatt, Dennis (April 1987), "How Klattalk became DECtalk: An Academic's Experiences in the Business World", The official proceedings of Speech Tech '87, New York: Media Dimensions Inc./Penn State, pp. 293–294
  6. ^ Computer talk: amazing new realism in synthetic speech, By T. A. Heppenhemimer, Popular Science, Jan 1986, Page 42 and 44 and 48, ..with the creator of DECtalk, Dennis Klatt...Ironically having given computers the power of speech, he slowly losing his own...DECtalk - actually a micro computer itself -...
  7. ^ Glenn Rifkin (December 16, 1990). "Technology; A Wider Work Force by Computer". The New York Times. the audience heard the DECtalk, voicing words that the educator typed into his computer.
  8. ^ Kari Haskell (December 12, 2002). "The Neediest Cases; Battling Federal Bureaucracy To Have His Benefits Restored". The New York Times.
  9. ^ Brian J. Edwards, ed. (February 1984). "DECtalk Speaks into the Future". HARDCOPY. pp. 84–85.
  10. ^ Stewart, Lawrence C.; Payne, Andrew C.; Levergood, Thomas M. (November 16, 1992). Are DSP Chips Obsolete? (Technical report). Digital Equipment Corporation. Retrieved March 23, 2024.
  11. ^ Hallahan, William I. (1995). "DECtalk Software: Text-to-Speech Technology and Implementation". Digital Technical Journal. 7 (4). Digital Equipment Corporation: 5–19. Retrieved March 23, 2024.
  12. ^ "AllLinuxDevices: Force to Support Linux On DECtalk TTS For Strongarm and Intel Devices". Linux Today. October 26, 2000. Archived from the original on May 18, 2014. Retrieved September 16, 2012.
  13. ^ "Fonix acquires DECtalk from Force Computers". Deseret News. September 16, 2012. Retrieved September 16, 2012.
  14. ^ "SpeechFX Text to Speech Solutions, FonixTalk, DecTalk". SpeechFX, Inc. April 19, 2021. Archived from the original on April 19, 2021. Retrieved October 8, 2023.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
  15. ^ "Voices Used in NOAA Weather Radio". Archived from the original on February 6, 2008.
  16. ^ US Department of Commerce, NOAA. "New NOAA Weather Radio Management Platform is Coming Soon". Retrieved May 5, 2019.
  17. ^ Hawking, Stephen. "Stephen Hawking and ALS". Archived from the original on April 26, 2021. Retrieved August 10, 2009. (Originally published as: Hawking, Stephen. "Disability - my experience with ALS". Archived from the original on June 14, 2000.)
  18. ^ Greenemeier, Larry (August 10, 2009). "Getting Back the Gift of Gab: NexGen Handheld Computers Allow the Mute to Converse". Scientific American. Retrieved August 10, 2009.
  19. ^ Lange, Catherine de (December 30, 2011). "The man who saves Stephen Hawking's voice". New Scientist. Retrieved June 9, 2013.
  20. ^ Hawking, Stephen. "The Computer". Retrieved March 1, 2015.
  21. ^ Fagone, Jason (March 18, 2018). "The quest to save Stephen Hawking's voice". Retrieved March 20, 2018.
  22. ^ "Plogue - chipspeech :: Vintage speech synthesizer". PLOGUE - Music Software - Developers. Retrieved April 27, 2016.
  23. ^ Karl Bartos, "Der Klang der Maschine". pp. 427–428. Retrieved August 25, 2017.
  24. ^ "El Rincon del UtaUtaUtau". Retrieved October 16, 2022.

External links[edit]