The Enterprex BJ-21 Black Jack calculator was introduced in 1978 and manufactured by Nam Tai Electronic Company Ltd. in Kowloon, Hong Kong. The BJ-21 has a sleek design and unique features, making it an interesting piece of technology from the late 1970s.
The calculator has a slim and tall profile, measuring approximately 80mm in width, 142mm in height, and 12mm in depth. It weighs 110 grams without batteries. The device is powered by two AAA batteries, providing 4.5V DC, and also accepts an adapter through a socket on the bottom side.
The case is made of smooth dark brown plastic, almost entirely encased in brushed aluminum panels with a gold tint. The front panel features black text, labels, and decorative symbols. The display is a 10-digit green Vacuum Fluorescent Display (VFD) with additional indicators for negative numbers, blackjack, and errors. The keys are concave, colorful, and have a short travel clicking mechanism, though their reliability can be inconsistent.
The Enterprex BJ-21 offers standard four-function capabilities, including addition, subtraction, multiplication, and division, along with square root and one level of brackets. It features a solid construction, giving it a substantial feel. The calculator comes with a bill-fold style wallet in brown plastic, equipped with a pen holder, a slot for the manual, and another for a notepad.
Internally, the calculator consists of several components:
- 1 x CPU: NEC D1021C K83216, 28-pin DIL, 0.6″ width.
- 1 x 12-digit VFD unit: Futuba 12-ST-22A 8D.
- 2 x transistors.
- 6 x diodes.
- 7 x capacitors.
- 4 x resistors.
- 1 x transformer: TDK CV-001.
The main CPU board sits loosely on top of the keyboard assembly, connected by 16 copper wires and fixed to the front with plastic lugs. The main board has cut-outs to accommodate capacitors, reducing the width of the assembly. Opening the calculator requires careful handling to avoid damage.
Logic:
- The (CE) key cancels the last entry, while the (C) key clears the entire calculator.
- Input overflow is suppressed; entering an eleventh digit is ignored.
- Negative numbers are displayed with a “-” sign in the immediate left digit, allowing for full ten-digit negative numbers.
- Automatic constant is available for all four functions.
- Dividing by zero results in a zero display with an “E” in the far left digit, and this error is not recoverable.
- Overflow shows the result with an “E” in the far left digit and can be recovered using the (CE) key.
- Negative square roots are allowed and result in a negative number.
- The percentage key, when used alone, divides by 100.
- In Game mode, the display splits into two sections: the dealer’s hand on the left and the player’s hand on the right. A full flashing display of zeros indicates a shuffle.
- The blackjack keys include: (BET) to place a bet, (HIT) to get another card, (STD) to stand, (INS) for insurance if the dealer has an ace, (SPL) to split a pair, (DBL) to double the bet, and (TOT) to show the total stake after a game.
The Enterprex BJ-21 Black Jack calculator is a well-built device with a distinctive design and functional features. Its ten-digit display and reliable logic make it a practical tool, while its game mode adds a unique twist, making it a versatile calculator from its era.
