Kenwood TM-621A Instruction Manual

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7-2. CTCSS unit TSU-6(TM-621A/721A only)The use of the optional sub-audible tone decoder TSU-6 al-lows for CTCSS (Tone squelch) operations. When this op-tion is activated the squelch of the SUB band will only openwhen the proper sub-audible tone is received.7-2-1,Caution:InstallationBeforeinstallation,besuretodisconnecttheDCpowercord,ordamagemayresult tothe transceiverortheunit.1, Loosen the 2x2 sidescrews.2. Remove the 2 screwssecuring the Top cover.3. Remove the 2 screwssecuring the rear panel.4. Gently remove the topcover. Be sure not todisconnect the wire tospeaker.5. Remove the backing fromthe cushion (small) thatwas provided the TSU-6and attach it to the backof the TSU-6. (Fig. 2)6. Attach the cable fromTSU-6 as shown in thediagram. (Fig. 3)7. Remove the backing fromthe other side of theloosen ?loosenZ saeCushion (small)cushion and attach theTSU-6 to the transceiver.8. Route the wiring as shownin the diagram. (Fig. 4)Chemical5 condenserFig. 49.Replacethecovers andtighten thescrewstocompletethe installation.7-2-2. Operation1. Press the VFO key toselect the VFO mode.2. Rotate the MAIN Tuningcontrol, MHz key, orMicrophone UP/DWNswitches to select thedesired frequency.(For example 146.520MHz)3. Press the F key and thenTONE/T.SELkey.Thecur-renttonefrequencywillbedisplayed.Rotate theMAINTuningcontrolorpress theMicrophoneUP/DWNswitchesuntilthe desiredtone frequency appearsinthe display.4.Press theVFOkeytoreturn theVFO mode.aATAKoo atedoc46520 rao33