Hi, I have had many requests to produce a mod for CTCSS Tone upon COS for the NHRC-4/M2 series controllers. Here ya go: http://www.repeater-builder.com/ge/mastrIInhrc-4-ploncos.html The link is also available from the NHRC Index page on RBTIP: http://www.repeater-builder.com/rbtip/nhrcindex.html Kevin Custer W3KKC