codes / PL tones

• CTCSS (Continuous Tone Coded Squelch System)
  CTCSS (Continuous Tone Controlled Squelch System) a sub audible tone in the range of 67 to 254 Hz. The FM deviation level of CTCSS tones should be in the range of 500 to 800 Hz. These tones are encoded with the voice audio at all times during the transmission. Any one or more of the 50 tones can be used to gain access to the repeater.
• CTCSS, PL, Tone Squelch, and other Necessary Evils
  Long ago and not so far away, Motorola came up with a way to get more than one Land Mobile customer on the same frequency at almost the same time. They figured that different customers could coexist on the same frequency if they did not have to listen to each other routinely. They invented Continuous Tone Coded Squelch System or CTCSS for short and patented it as "PL" short for "Private line". Other manufacturers, finding that the system was absolutely necessary to stay competitive came up with "Channel Guard," "Quiet Channel," "Call Guard," and many other names for the same thing to avoid lawsuits for marketing a patented system.
• DCS - Digital Coded Squelch
  DCS (Digital Coded Squelch) is digital data or code word that is transmitted with the voice audio. Unlike CTCSS (Continuous Tone Coded Squelch System) which uses continuous tones below 300 Hz., DCS uses digital data or code words. Each code word is unique and all code words may be used on the same channel without interference.
• Improved PL Tone Encoder
  N1HFX improves on the old PL tone design.
• Motorola CTCSS Code Equivalents
  
• PL Tones
  PL Tones (Private Line, a Motorola Trademark) are used to control repeaters, exclude foreign traffic and control remote sites throughout the Public Safety and business two-way world. Common conventional PL Codes and the Digital PL Codes are listed.
• PL Tones
  PL tone frequencies with corresponding Motorola, Icom, GE, and Yaesu designator codes.
• The Really Useful Neat Stuff Page
  Information on CTCSS, DCS, (Motorola trade name DPL - Digital Private Line), Paging Tones, and DTMF.