Continuous Tone-Coded Squelch System

The CTCSS function ( Continuous Tone Coded Squelch or Continuous Tone Coded Subaudio Squelch System) ( subtone squelch method; IE code, pilot tone ) allows selecting specific wireless devices within a selected channel. When sending a low tone is also transmitted ( pilot tone ), respond to only the radios that are programmed on this ringer from the caller. When arriving the Erkennungstons they are then open the reception for listening.

Audio frequencies

CTCSS transmit simultaneously with the useful signal control sounds ( 67-255 Hz - low tone ). The tones are at the lower end of the audible frequency spectrum. Normal radios suppress such deep tones and usually give only 300 Hz to about 3000 Hz from the speaker. The frequencies of each stand to each other in conditions crooked to not arise by mixing other CTCSS tones can. CTCSS signals are used for the squelch control ( Squelch ) of the receiver. Only when the received signal mitsendet the matching CTCSS tone with the useful signal, the squelch opens.

The frequencies of each note (pitch of the CTCSS tone ) are:

The 39 tones after TIA/EIA-603-D are in bold.

The frequencies at which the different CTCSS tones are sent, are identical with the radio frequency.

Synonyms for CTCSS

• Channel Guard ( CG) - is the abbreviation for General Electric;
• Private Line (PL) - is the abbreviation of Motorola; the corresponding sound is the PL tone;
• Interference Eliminator Code - is the abbreviation of Motorola ( 2006);
• Quiet Channel ( QC) - is the abbreviation of the RCA ( Radio Corporation of America );
• IE code
• Pilot tone

Radio

CTCSS is used, mutual interference between multiple co-users to minimize the same frequency. For example, the accessible for everyone PMR uses only eight channels. The channel but again 38 " subchannels " encoded by CTCSS. CTCSS thus acts as a selective call. A signal is continuously broadcast with sending. Must be distinguished from Selcal (also a selective call ), in which only the beginning of the mission, a code signal is sent to turn off the receiver squelch ( squelch ). As the name CTCSS ( Continuous Tone Coded Squelch System) suggests, it is a continuous tone. In contrast to the usual squelch ( squelch system ) comes when CTCSS but no sound from the speaker when the code signal is not true, or not detected due to weak signals. The advantage of CTCSS is that your device radio is absolutely still during the reception standby, which creates a relaxed atmosphere for the radio operation.

The Sende-/Empfangsumschaltung happened absolutely still. The voice of the other party is just so out of the receiver's speakers without the usual cracking when opening and closing the squelch. This is achieved in that first the substrate is scanned and only a short time later ( 0.1 seconds ) of the CTCSS tone is keyed to the carrier. The speaker of the receiver so only opens when the transmitter is already at full capacity. To receive switch the CTCSS tone is also only taken from the carrier, so that can switch off the speakers of the receiver. Only after the transmitter is switched off. There is no Nachrauschen ( Noisetail ) more in the receiver.

When CTCSS all remote stations must be equipped with CTCSS to evaluate the pilot tone CTCSS and turn on the loudspeaker at the receiver match. Sent by the sender no or other CTCSS subtone, the speaker remains silent at the receiver. If another receiver is listening on that frequency and turned on at all no CTCSS subtone has (or his device does not have this function), then he can listen in without any problems. However, it may the CTCSS transmitter does not respond, because these only hear radio messages that are backed by the right CTCSS subtone.

An eavesdropping does not offer this function, since the voice sending is not encrypted or encoded. Only the ( inaudible ) pilot tone is added, but the language itself remains unchanged clear.

But the trouble- free use of a frequency of many fellow users with different CTCSS Subtoneinstellung relates only to the hearing. When you send can be seen on a frequency that is used by very many people quickly become a jammer, if you put into radios in the current program of another. In radio traffic without CTCSS can hear if someone else is speaking at the frequency. When CTCSS you just do not listen when someone speaks another on the frequency. If you have switched to another subtone, then you hear nothing from the other, even if the frequency is in use. CTCSS capable radio devices have therefore usually one indicator which lights when the channel is currently busy. At this moment, you should not send them, as they act against each other as each other jammers. In operation, the wireless device can be programmed to do that for an occupied channel can not be sent with the wrong CTCSS tone. In radio traffic without CTCSS occurs in jamming audible noise (whistling ). When CTCSS radios can be heard at a Jamming nothing if is not detected due to the interference of the pilot tone and mutes the radio therefore.