The Corvus 415 caclulator was released in 1974 by the Corvus Corporation – a consumer division of the semiconductor giant MOSTEK. With dimensions of approximately 76mm x 150mm x 36mm and a weight of 216g (including rechargeable batteries), it feels sturdy yet portable, designed to function equally well as a handheld device or a desktop tool. Its wedge-shaped profile and rounded edges prioritize ergonomics, while the matte beige plastic case and brown leather-effect keyboard surround lend an understated sophistication. The keyboard has soft-touch, “bouncy” keys and a prominent brown-and-silver brand plate above.
At the heart of the Corvus 415 is an 8-digit red LED display, supplemented by a ninth digit for signaling errors, negative values, or memory status. The display’s red plastic filter is deeply inset and angled, ensuring visibility from a wide range of perspectives. Below it, the calculator’s interface includes standard four-function operations, percentage, reciprocal (1/x), memory functions, and a register exchange key—a feature that sets it apart from earlier models like the Corvus 310 and 320.
Power comes from a 6.0V DC rechargeable battery pack (four AA cells) or an optional adapter, though users are cautioned against operating it on battery power for more than 12 hours to avoid damage.
Internally, the Corvus 415 relies on a Mostek MK50203N single-chip calculator circuit, paired with an ITT 508N 7430 IC and a compact array of components: one transistor, two capacitors, ten resistors, and a specialized transformer. The main PCB floats within the case, anchored by pillars and rear screws, while the keyboard is secured with adhesive—a design choice that hints at cost-effective manufacturing.
Disassembly involves removing four screws, revealing a construction that prioritizes simplicity over repairability.
Logic
- (C) key: Cancels incorrect numerical entries on the first press; clears the entire calculation on the second.
- Input overflow: Ignores ninth-digit entries, capping input at eight digits.
- Automatic constant: Activates only for multiplication and division.
- Negative numbers: Displayed with a minus sign that shifts into the ninth digit, allowing full eight-digit negative values.
- Divide by zero: Returns zero and triggers an “n” in the ninth digit; unrecoverable without resetting.
- Overflow errors: Show “n” (or “0” for negative overflow) in the ninth digit; also unrecoverable.
- Memory errors: Storing values like 99,999,999 twice can lock the calculator, requiring a (CM) press to reset.
- Memory indicator: A lowercase “L” appears in the ninth digit when memory is in use.
- Percentage key: Divides the current number by 100 on the first press only.
- (EX) key: Exchanges registers to invert division calculations.
The Corvus 415 is a thoughtfully designed calculator with a focus on tactile feedback and visual clarity. Its robust logic system handles everyday arithmetic competently, though its lack of error recovery—a common limitation in early calculators—can frustrate modern users. The 415 came with a brown vinyl carrying case with a cotton liner and partial zipper. Its historical significance as a MOSTEK product adds collectible appeal. While not groundbreaking, it represents a reliable iteration of 1970s calculator technology, balancing form with function.
