Over The Air Bitmap Image (.otb)
The OTB (Over The Air Bitmap) file extension, developed by Nokia, is used for transmitting black and white bitmap images between mobile phones, particularly Nokia and Siemens models. These images, with a maximum resolution of 255x255 pixels, are often sent via SMS in either hexadecimal text or binary format. Historically, OTB files were popular in the early days of mobile communication for sending simple graphics, icons, and wallpapers when data transmission speeds were limited.