Brother 408AD

The Brother 408AD is a handheld calculator from the mid-1970s. It measures approximately 78mm x 142mm x 15-20mm (width, height, depth) and weighs around 120g without batteries. Power is supplied by two AA batteries or optionally by an AC adapter.

The 408AD has a rectangular case made of matte black plastic with a brushed aluminum wrap-around front panel. The inset green display filter makes the 8-digit vacuum fluorescent display easy to read. It displays up to 9 digits, with the 9th used for negative signs and error codes. Keys are oval shaped with a soft touch.

Functionality is fairly basic – it supports the four standard arithmetic operations, percentages, square root, pi, and sign change. There is a constant feature for repetitive calculations. Input overflow is not suppressed, allowing entry of more than 8 digits. Errors like divide by zero show an error code in the 9th digit but are not recoverable.

Inside, the main board is labeled BP-2176-1 and uses a NEC uPD940C processor. The keyboard connects via a ribbon cable and is labeled BP-2177-1. Other components include a custom 9-digit VFD, transistors, diodes, resistors, and capacitors.

The 408AD was manufactured in Japan by Brother Industries Ltd around 1976, as evidenced by the serial number on this example. The original case design featured an open top with half-moon cutouts, but was a bit undersized.

While well constructed, the lack of features like a memory and full input overflow suppression seem like odd omissions for the mid-1970s. The ability to enter negative numbers was also unusual. But the 408AD provides the basic functionality needed for most calculations in an attractive desk style case.

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