A landmark cassette recorder for the technology included in a fairly small box and excellent design which came well in sync with the timeframe - one which vanished all too quickly.
Driving the tape is a Quartz-locked, Direct-Drive, planar-opposed, DC brushless, slotless motor.
The rotor magnet and stator coils are placed in planar opposition while the capstan (an integral part of the rotor / flywheel) is drawn toward the stator by the rotor magnet for absence of mechanical play toward the capstan thrust.
The second motor -for the reel drive- is a coreless DC micro-motor.
The transport pads only need 80g of pressure (0,7mm stroke) to activate. All this can be controlled at a distance by way of the RP-9690 wired remote control or later RP-070 semi-wireless.
PNP / NPN two-stage audio amplifier, a beautiful glass-encased FL display and Laminated Sendust (SX) complete the picture.
Briefly updated in 1979 as RS-M85MK2 outside Japan : still brown but with an extended front for 19" rack mounting and having METAL tape compatibility by way of the bias adjust pot which could be pulled for Type IV tapes.
The RS-M85MK2 was also available as an RS-M88 : brown or silver color depending on market (Japan = brown, Europe = silver) but sans extended front.
Added on both MK2 and 88 versions was a blue dot on the eject button - too many people turned the deck off instead of ejecting the tape ;-)
The RS-M85 was "only" a two-head deck - the real topper was the rare RS-M95.