Orgtehnika ELKA 135
Brief History
Almost all of the first bulgarian pocket calculators used Rockwell ICs, except the first scientific model, the Elka 135, which contains a General Instrument circuit. Design and construction are almost the same as earlier Elka 101, but the wider LED display module needed new window. The redesigned front became more aesthetic and popular in the western countries too. Interestingly, the exponent enter key has only an E letter on it. One year after this model was replaced by Elka 135m, which uses Rockwell circuit.
| Manufacturer: | Завод Оргтехника Силистра (Bulgaria) |
| Mfg. date: | 1975 |
| Size: | 7×13,6×3 cm |
| Weight (ready for operate): | n.a. |
| Type: | scientific |
| Capacity: | 8/5+2 digits (input/display) 8+2 digits (internal precision) |
| Operating logic: | algebraic |
| CPU: | General Instrument C596 |
| Registers: | 2 standard (with saving the pending operation) 1 constant (with saving the pending operation) 1 memory (with aritmetic) |
| Features: | +/-change sign (direct entry of negative numbers) Ffloating-point notation Sciscientific (exponential) notation Sqrsquare root pivalue of pi (3.1415..) can be recalled 1/xreciprocal trigtrigonometrical functions (sin, cos, tan and inverses: arcsin, arccos, arctan) logexponential and logarithmical functions (10- and e-base) |
| Display: | 9 digit LED (Bowmar Optostic) |
| Power: | 4×AA-type battery 6V adaptor |
| Test results: | trigonometry:result of sin-1(cos-1(tan-1(tan(cos(sin(60°)))))), reference value: 60. 67.497 exponential:result of 0.999160000, reference value (first 14 digits): 3.0068804206375×10-70 3.007E-70* |
ELKA 135
PCB of the ELKA 135
Inside of the ELKA 135
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