Talk:Professional mobile radio
say why subaudible tones subaudible
Mention more about subaudible tones. The UNIX beep(1) man page says middle C octave starts at 261.6 Hz, and I can do "beep -f 111" and can't our ears hear from 20-20000 Hz when young at least. --User:Jidanni 2006-11-16
Because most modern mobile radios filter tones below about 300Hz. --18.104.22.168 15:30, 1 June 2007 (UTC)
"As there is no incremental cost for the transmissions that are made, individual calls are not charged, but instead there is a rental for overall use of the system."
- Is this correct? With the use of MPT1327, TETRA etc users can be charged by usage and probably are on some systems. If the UK emergency services AIRWAVE system is included then they are very definitely charged by usage, so much so that users have been instructed to keep their calls short according to press reports. --jmb 10:40, 16 September 2007 (UTC)