Telecommunication
The other meaning of the term "channel" in telecommunications is seen in the phrase communications channel, which is a subdivision of a transmission medium so that it can be used to send multiple streams of information simultaneously. For example, one radio station can broadcast radio waves into free space at frequencies in the neighborhood of 94.5 MHz (megahertz) while another radio station can simultaneously broadcast radio waves at frequencies in the neighborhood of 96.1 MHz. Each radio station would transmit radio waves over a frequency bandwidth of about 180 kHz (kilohertz), centered at frequencies such as the above, which are called the "carrier frequencies". Each station in this example is separated from its adjacent stations by 200 kHz, and the difference between 200 kHz and 180 kHz (20 kHz) is an engineering allowance for the imperfections in the communication system.
Raszyn radio transmitter
The longwave transmitter Raszyn was until the inauguration of Warsaw radio mast in Konstantynów the central longwave broadcasting of Poland.
Since 1978 from this facility during daytime a second program in the longwave range was transmitted on AM-LW (long wave)198 kHz/1515 meters (formerly the frequency was used by Radio Parlament).
After the collapse of Warsaw radio mast in 1991 this facility was used until the inauguration of the new longwave-transmitter Solec Kujawski for transmissions of the first program of the Polish Broadcasting Service on AM-LW (longwave) 225 kHz/1333 meters. Because it was not possible to transmit from Raszyn on both longwave frequencies of the Polish Broadcasting Company simultaneously, no transmissions on the second longwave frequency of the Polish Broadcasting Company (AM-LW 198 kHz/1515 meters) took place between 1991 and 1999.
The radio mast of the longwave transmitter Raszyn is since the collapse of the Warsaw radio mast the sixth tallest structure in Poland. On July 31, 2009 Polish Radio Parlament on has discontinued their broadcast on AM-LW (longwave) due to economical crisis, and the longwave transmitter has been turned off.