The Executel, referred to as the “world’s most advanced executive communications unit,” integrated a phone and a computer, complete with a full QWERTY keyboard and a 5-inch black and white CRT monitor. It was able to store a whopping 235 phone numbers, had a robust calendar feature, and could be used as a notepad or an electronic diary (for 20 years, according to the advertising jargon). A mini-cassette tape stored all the data. Since was 1984, the age of advanced consumer technology was just beginning to dawn, so this was big-time innovation!
The Executel phone could be operated on “hands-free” mode to use its many fancy computer features simultaneously. Short-cut keys for quick and easy access to the calendar functions were surely an essential feature that all “top executives” needed to properly schedule their meetings and appointments.
STC called it an “integrated, multifunctional, network-linked, public-data, desk communication telephone.” Since it was hard-wired to a landline, it was relegated to whatever dial-up networking was available at the time. An ad brags about its ability to dial and redial numbers with the touch of a single button. If you ever had to use a rotary phone, this was actually a wonderful invention.
According to YouTuber Techmoan, only 5,000 were sold in the UK for about 1,400 pounds. It was never sold in the United States.
Source: https://www.slashgear.com/948575/the-stc-executel-was-one-of-the-first-smartphones-in-1984/