In 1986, a structure was introduced that improved resistance to vibration and shock. The smaller size of the casing allows for a design that ensures stability when carried.
D-55T
The D-55T is the early Discman that brought Walkman-style convenience to CD playback by adding an AM/FM tuner with television audio band support. The lid served as a full tuning scale and the headphone cable doubled as the antenna, while mono/stereo switching and local/distance tuning made the radio side more than a novelty even if reception still depended heavily on where you were listening. Sony understood very quickly that convenience mattered almost as much as digital novelty. The core CD hardware stayed close to the D-50MkII, but the added tuner changed the personality of the machine. This is the kind of player that made more sense in a commute bag or on a trip, where carrying one device that could cover both discs and radio started to matter.
D-100
The D-100 is a model that expands upon the functionality of early portable CD players while miniaturizing their configuration. It features playback control functions such as program playback, repeat playback, and A-B repeat, and the transport mechanism has also been miniaturized. The power supply relies on an external battery and it does not have a vibration-resistant mechanism. Although improvements have been made to accommodate portable use, it is intended for use in a stable installation environment. It is an advanced model of the early generation that aims to balance miniaturization with added functionality.
By 1986, the difference between sound quality and portability had narrowed. However, the device's structure was still in a developmental stage.
