The MK 235 cassette recorder (sometimes referred to as “ZRK MK 235” or “MK 235 Automatic”) was manufactured in 1976-1978 in Zakłady Radiowe im. Marcina Kasprzaka in Warsaw. The portable cassette recorder, positioned on the boundary of popular and standard product classes, was designed to record sound and play back recordings. Its design was based on the licensed C-235 model by Grundig. It incorporated transistors and an integrated circuit. The MK 235 is powered from an AC source or batteries (five R14 type batteries). Operation time using batteries is about 14 hours. The tape recorder is designed to play cassettes at a tape speed of 4.75 cm/s.
The device is made of black polystyrene and has the shape of a flat cuboid. In the top part there is a slide-out handle, a play button, a sideways fast-forward/reverse button, a stop button, a red recording button, and two potentiometers – one for volume and one for tone. The front face is divided into two roughly square areas. On the left, there is the white cassette tray behind acrylic glass and the eject button. Inside the tray there is a two-track play/record head. On the right, behind a perforated grille, is an oval speaker, and a microphone is placed in the upper right corner. A Grundig logo is placed in the bottom left corner. On the right side there is a multi-purpose connection socket with a microphone, radio, or gramophone input, and a mains socket. At the back, in the lower part of the housing, there is a battery compartment.
The aesthetics of the device are minimalistic, dominated by the geometry of its overall shape. Its form is livened up by the rounding of its edges, using geometric shapes and grooves to divide the planes. The lightness and reliability of the device are emphasised by contrasts of materials used in its design, as well the colours: black, white, and metallic (thanks to the use of aluminium components). Also contributing to the attractive appearance of the tape recorder are the thin black lines on the handle, a white line forming a square around the cassette tray, an aluminium decoration in the form of a stripe above the cassette tray, and the microphone grille with two rows of symmetrical, horizontal slits, whose length is similar to the diameter of the perforation holes in the speaker grille.
The cassette recorder is a simplified version of the MK 235 model. The first batch launched on the market had a battery charge indicator on the right side of the top, next to the potentiometers. The original version had only “Grundig” and “MK 235 Automatic” inscriptions. The text “Unitra ZRK” only appeared on the housing in the 1978 version.

Authors: Filip Wróblewski