The CD 400 is a second-generation machine, constructed entirely of SSI ICs.

It appears to be a follow-on to the ICR-412, also found on this site.

Like the ICR-412, The circuit boards carry the Japanese-language "National" logo indicating that the electronics were produced by Matsushita as an OEM for Olympia. Internally the CD 400 is similar to the Panasonic 1200 although the latter machine appears to have shift register memory in place of an acoustic delay line. National and Panasonic were both brand names used by Matsushita.

The CD 400 is a basic 4-function, one memory machine.