This CTCSS encoder can be installed in any transmitter, connecting the Tone Output to the audio modulator circuit after the microphone amplifier. CTCSS is an Abbreviation of Continuous Tone Controlled Squelch System and was introduced to allow several groups of users to use the same frequency without the groups hearing each others conversation. There are 42 sub audable tone frequencies allocated for CTCSS use in the PMR world and 9 in the amateur radio world. This circuit was designed to enable me to access the local 2mtr amateur radio repeater on 145.750MHz using a CTCSS sub audable tone of 94.8Hz. As you can see from the charts below any of the 42 CTCSS tones can be enabled. Most frequencies listed in the database on this site include the CTCSS tone if there is one allocated. Parts available from JAB Electronics - Birmingham 0121 681 1329.
This page was updated on 23th May 2000.