The Clever 2101 calculator, introduced around 1978, is a compact and unusual model that bears similarities to other calculators of its time, such as the Decimo Vatman Mini MII. This calculator is a product of Clever Electronic Calculator, although the specific manufacturing details remain obscure, with some speculating that it may have been produced by Detron of Korea. The Clever 2101 is notable for its unique design and functionality, which we will explore in detail.
Design and Construction
The Clever 2101 calculator measures approximately 73mm x 117mm x 19mm (width x height x depth) and weighs a mere 78 grams, excluding batteries. Its power source is a single 1.5V DC AA battery, with an option for an adapter/charger through a socket located on the top left side. The calculator’s case is a two-piece construction featuring glossy black and off-white plastic with a prominent rim around the edges. The top panel is adorned with a full-width black printed aluminum plate that sits in its own recess, displaying the model name.
The display is an 8-digit blue Vacuum Fluorescent Display (VFD) with an additional ninth digit for negative, memory, and error indicators. While the display is functional, the filter allows too much light, which can sometimes expose the display excessively. The keyboard surround is a recessed, matching brushed aluminum panel, and the concave keys are light-touch and springy, providing a soft click when pressed.
Components and Board Layout
The main components of the Clever 2101 include an NEC D1803C E8397D CPU, a 9-digit VFD, two transistors, five diodes, five capacitors, two resistors, and a transformer. The main board, labeled 51202, sits atop the keyboard assembly, which is secured to the front with ten screws. A 15-way ribbon cable connects these components. The transformer is strategically placed in its own cut-out to maintain the board’s slim profile.
Disassembly
To disassemble the calculator, one must remove the single screw from the back and gently pry off the front, starting at the bottom. There are two lugs on either side, and eventually, the front can be hinged around the top area and removed to the right.
Logic
- The (C/CE) key is used to cancel an entry, while a second press clears the entire calculator.
- Input overflow is suppressed; inputting a ninth digit is ignored.
- Negative numbers are displayed with a “-” in the far left (ninth) digit, allowing for full eight-digit negative numbers.
- There is automatic constant functionality on multiply and divide only.
- Overflow shows the result and “C” (or “E” if negative) in the far left (ninth) digit and is not recoverable.
- Divide by zero shows zero and “C” in the far left (ninth) digit and is not recoverable.
- Negative square roots are not allowed and result in zero with “C” in the far left (ninth) digit and are not recoverable.
- Memory store is indicated by the decimal point of the far left (ninth) digit.
- Overflow in memory retains the original number.
Summary
The Clever 2101 calculator is a small, unique model that offers standard four-function capabilities along with percentage, square root, and memory functions. While its low-contrast display filter is a drawback, the calculator’s logic is robust, albeit limited by the lack of recovery from certain error states. Overall, the Clever 2101 is a fascinating example of late 1970s calculator technology, showcasing both the innovations and limitations of the era.
