So much has bluetooth technology been popularized that most people, probably, haven't heard of DECT. Before there was a thing called "Bluetooth", DECT cordless was king of wireless! DECT made wireless landline telephony a reality, just like Wifi did for the Internet. Both DECT and Wifi were rolled out during the early 1990's; whereas Bluetooth was first introduced just after the turn of the century in 2001. Bluetooth is literary everywhere, used for computer peripherals, headphones and portable speakers by the vast majority of manufacturers, aside from - ONEaudio - who are resurrecting DECT, bringing it to the forefront as an alternative to Bluetooth audio. 
The first DECT cordless speaker that ONEaudio launched was the ONEmicro which was featured on Gadget Explained 5 years ago. The second generation ONEmicro, it's an upgraded version called ONEmicro Plus, which are the green and black color speakers seen pictured. Being DECT speakers, audio is transmitted via 1.9 GHz radio frequency, which is a stronger signal than Bluetooth and also more stable because DECT radio frequency does not compete with bluetooth peripherals.
Design wise, the ONEmicro Plus has the same cast iron metal body and metal grille mesh as the original ONEmicro with an status led ring built-in around the rubber base of the speaker. The status led flashes blue and red during pairing mode and show solid blue when connected. During audio playback, the status led turns off automatically (unlike the original ONEmicro) and will only light up when changing settings like volume or sound timbre.
The bottom of the ONEmicro Plus is rubberized and integrates two physical plastic buttons, which are slightly recessed to allow the base of the speaker to sit completely flush against the surface. The charging port is located on the bottom rim and has not been upgraded; hence it still uses a micro USB port. Each ONEmicro Plus speaker incorporates a 1000mAh rechargeable battery that takes 4 hours to recharge via 5V/1A (there is no fast charge support). From a single charge, you can get up to 11 hours of playtime on moderate volume (50%), which is twice the battery life you could get with the first-gen ONEmicro. You can get up to 20 hours when setting the volume source to 40% volume and leaving the speaker at default volume.
The ONEmicro Plus speakers can be used while charging but, they cannot be used like wired speakers because the ONEmicro Plus micro USB port is for charging only. There is no AUX audio port either, which would have been a neat upgrade. The ONEmicro Plus speakers no longer support ECO mode, although battery performance is better, thanks to a more efficient DSP chipset.
The buttons control the volume, as well as sound timber selection: Natural (no signal processing), Clarity, Vocal (emphasizes vocal sound in audio) and Comfort. Both Comfort and Clarity sound timbres emphasize speech when watching videos. Other functions you can control include left/right balance (up to 7dB), pairing mode and report status, which tells you the battery left in the speakers, as well as the sound timbre and left/right balance setting.