Sinclair launched the first in a range of Cambridge models in August 1973. They weighed less than 3.5 oz, cost £43.95 and measured just 50 X 111 X 28mm. The first models were basic 4-
This model came in 4 incarnations -
The Type 1 and Type 3 had K (constant) keys.
Type 2 had C and CE keys.
Type 4 had % key. It is also the rarest of the Cambridge range, presumably because by 1977 ,the design was 4 years old and LCD calculators from Japan were becming available and so relatively few were sold.
All came in a polystyrene-
These explained how to do constant arithmetic and reciprocals, and had examples of how to perform currency conversions, mortgage interest repayment, and compound interest.
Cambridge Type 1 model
Cambridge type 1 box
Cambridge display was 8 digit red LED
Type 2 model in brown plastic case.
Type 2 model
Type 3 model and box
Type 4 model
The Type 4 model was distinguished by having a % function!
This model came in three variations -
The Type 1 took 4 x AAA batteries, had 4 functions and an RM/CM key (one press recalled from memory, two presses cleared the memory).
The Type 2 took 2 x AAA batteries, and in addition to the Type 1 abilities, had a % key.
The Type 3 took a 9V PP3 battery, and had M, C/CE and % keys. The rear of the case had to have a bulge to accommodate the large battery.
Cambridge Memory Type 1
Type 1 distinguished by it's blue number keys and power button.
Memory Type 2 model and box
Memory Type 2 had a silver finish.
Memory Type 2
Memory Type 3 model, from around 1976, distinguished by unusual orange case!
Launced in March 1974 at a cost of £49.95, it was a development of the Cambridge with the same case but the addition of some scientific functions such as logarithms, trig, square root and pi.
Took 2 X AAA batteries and there was a switch to select degrees or radians inside the battery compartment.
Display was exponent format.
On 1st September 1976, the Cambridge Programmable was released (marketed in the United Sates as the Radio Shack EC-
It had an 18 byte memory allowing a 36-
It took the larger 9V PP9 battery which resulted in the bulge at the rear (below).
Bulge to accommodate PP3 battery.
Presentation box and manual.
Also had the bulge at the rear to accomodate the 9V battery.