The AEA HL-6 uses TTL (transitor to transistor) logic to communicate with your HF rig. I use the AEA RL-1 on a regular basis and is the same thing as the HL-6 but uses 70cm for the control frequency and 2mtrs to hear what the HF rig is hearing as opposed to calling CQ using your phone line. Best to do this alone if you get my drift. People may think your strange. The HL-6 and Rl-l will not work with any radio that I know of that uses the 9 pin D serial interface port, such as the Kenwood 570 and 870 etc, the logic levels are wrong. I know this cause I have a 570 and tryed about every possible configuation method. Even with a level converter I have never gotton the RL-1 to accept the DTMF commands, or during the programming sequence get it to recognize my TS570SG to have full remote control of tuning, band changes, modes, etc. They do work perfectly with my Kenwood TS450 and the 850. Heres a list of the radios I believe the HL-6 will work with. Older Icoms with TTL logic interface (models unknown) Kenwood TS140, 440, 680, 711, 811, 940, TS50 w/interface option, TS450, 850, and 950. Yeasu FT-890, 990, FT-747GX, 757GXII, FT1000 I have messed around at length with the RL-1 and made many contacts using a fully programable remote control of my base station (Its like being there but your not there) and the HL-6 looks to be fun as well if you can find them. Both are rare today! Hope this helps. Good luck!