Konftel 300. Display: LCD, Display resolution: 128 x 64 pixels, Display size (HxV): 63.5 mm (2.5 "). Frequency range: 200 - 3300 Hz, Microphone frequency: 200 - 3300 Hz. Interface: RJ11 / USB 2.0 Mini B. Weight: 1000 g. Operating temperature range (T-T): 5 - 40 °C, Operating relative humidity range: 20 - 80 %