Abstract: A transmitter of a cognitive radio comprises a selector for selecting from a memory a channel which is determined free, for a power measurement. A power meter measures the received power from the selected channel. Detection selector compares the measured power and a power of the same channel saved in the memory and selects the channel for detection if the power in the channel is within a predetermined range from the power saved in the memory. A detector performs detection of the channel as a response to the selection for detection. A channel selector selects the channel for communication if the channel is detected unoccupied on the basis of detection. The transmitter communicates in the channel as a response to the selection for communication.

Abstract: A transmitter of a cognitive radio comprises a selector for selecting from a memory a channel which is determined free, for a power measurement. A power meter measures the received power from the selected channel. Detection selector compares the measured power and a power of the same channel saved in the memory and selects the channel for detection if the power in the channel is within a predetermined range from the power saved in the memory. A detector performs detection of the channel as a response to the selection for detection. A channel selector selects the channel for communication if the channel is detected unoccupied on the basis of detection. The transmitter communicates in the channel as a response to the selection for communication.

Abstract: Method for producing a raster surface for use in the coloring of a contact lens, in which method an image surface consisting of picture elements is selected, the image surface is subjected to a tonal reduction operation and a threshold tone value is defined for it, and picture elements darker than the threshold value are made black while picture elements lighter than the threshold value are made white, and the black-and-white image surface is subjected to radial stretching in relation to a given point, the position of said point corresponding to the center of the contact lens to be treated, whereupon a raster pattern for the image to be created on the contact lens can be produced using the image surface, i.e. raster pattern thus obtained.