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.
Warsaw radio mast
After the collapse of the radio mast at Konstantynów, the Polish broadcasting company used the old Raszyn transmitter with its mast near Warsaw, which had been used since 1978 for daytime transmissions of a second Polish broadcasting service programme in the longwave range on the frequency AM-LW 198 kHz, for transmissions on AM-LW 225 kHz with a power of 500 kilowatts. It is not possible to transmit from Raszyn on AM-LW (long wave) 198 kHz/1515 meters and 225 kHz/1333 meters simultaneously, so the transmissions on the second longwave frequency AM-LW (long wave) 198 kHz had to be discontinued until either a second longwave broadcasting transmitting facility was built in Poland or a special frequency switch, which would allow transmissions on both frequencies, was installed at the Raszyn transmitter. The latter, simpler solution would have decreased the effectiveness and reliability of both transmitters and was therefore found unacceptable.