Sinclair Cambridge models
The Sinclair Cambridge was introduced in summer 1973, and was the first of a range of a dozen models and variations.
This page illustrates the several varieties of the basic Sinclair Cambridge calculator, which can be distinguished by the key arrangements.
Here are what we believe to be all of the models in what we think is their
chronological order.
Sinclair Cambridge type 1
Sinclair Cambridge (type 1).
8 digits, red LED.
4-functions, constant.
Has [C] and [K] (constant) keys.
Batteries: 4x AAA.
Main integrated circuit - General Instruments Microelectronics GI-C550, here date coded mid-1973.
50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").
Made in England.
The first of the very small Sinclair Cambridge series, introduced in Summer 1973, costing in Britain £43.95 Sterling (US$105).
The case has a glossy finish, with a poorer quality moulding than usual for Sinclair. The main chip is in a more expensive ceramic package.
Sinclair Cambridge type 2
Sinclair Cambridge (type 2).
8 digits, red LED.
4-functions.
Has no K (constant) key, but has automatic constant on all functions i.e. the second operand of all calculations is automaically stored as the constant factor.
Has [C] and [CE] (clear last entry) keys.
Batteries: 4x AAA.
Main integrated circuit - Texas Instruments TMS0801NC, here date coded end of 1973.
50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").
Made in England.
Sinclair Cambridge type 3
Sinclair Cambridge (type 3).
8 digits, red LED.
4-functions, constant.
Has [C/CE] (one press clears last entry and two presses clears everything) and [K] (constant) keys.
6v (4 x AAA).
Main integrated circuit - General Instruments Microelectronics GIMT-CZ550,here date coded to the end of 1975.
50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").
Made in England.
A later, more common, version of the Cambridge.
Sinclair Cambridge type 4
Sinclair Cambridge (type 4).
8 digits, red LED.
4-functions, %.
Has [C], [CE] (clear last entry), and [%] keys.
Batteries: This model takes only 2x AAA.
Main integrated circuit - General Instruments G-595, here date coded to the end of 1975.
50 mm x 111 mm x 28 mm (2" x 4.4" x 1.1").
Made in England.
Note the use of LED displays made by Bowmar, the pioneering U.S. calculator manufacturer.
When first introduced in summer 1973 the Cambridge cost £43.95 Sterling [about US$100].
In Summer 1977 the mail-order discount price had dropped to £8.95 Sterling [about $US15].
