When I read about the external switch to control the DVR memories in my 756 Pro II, and not to have to be in the DVR menu, I knew I had to have one.

The 4 push buttons on top of the unit control the 4 DVR memories as well as the 4 CW memories regardless of the currently displayed menu. This unit does more than control the 4 memory buttons. The large horizontal toggle controls 2 relays, 1 DPDT and 1 SPDT relay. The DPDT moves the audio and audio ground between the IC-756 Pro II and the FT-857, the SPDT moves the PTT line from my homebrew handswitch to the PTT of each radio. It runs off a 9V WalWart.
I have plans to add a line converter for the 857D and drill another hole for serial cable to the PC, and I will have PC control on the 857 while using the HC4

UPDATE, I found an easier way for the 857D level converter. I placed an 8 conductor baseboard jack in the mic line to the 857D. Inside the jack is the simple 2 transistor level converter circuit that goes to the mic jack of the FT-857D. An undocumented feature on the 857D is the fact there is a serial input and output on the mic jack. Using this port for CAT allows you to have the rig hooked to your PC and have the Linear/Tuner/Cat jack on the rear free for other uses. In addition this setup allows me to use my HC4 on a boom, or should I desire, I can quickly plug in the stock hand mic and still have PC control on the both of them. I have really enjoyed this mic switch, it works great and the Goldline really makes the 857D sound a lot better than the little hand mic. The Switch has a 1/8" phone jack on the rear that I plug the Goldline or the Headset into, I use tip and ring to isolate the mic and mic ground from the case of the switch. No RF problems, works like a champ. When I first designed the switch I thought about putting an 8 pin Foster connector on it but it occured to me, WHY? We only need mic and mic ground. Besides the Headset already used a 1/8" male phone into an 8 pin Foster adapter! It saved a lot of money and makes switching the mics VERY fast! Now the adapter is in the junk box!
Icom CT-17 (PC control for 4 radio)
I looked at many used CT-17's and almost bought one on a couple of occasions. I downloaded the manual in anticipation of buying one. Once I looked at the manual and saw the schematic I noticed there was nothing to it! I began ordering parts off Mouser. When I was finished, it totaled a whopping 16 dollars!! I put it together by copying the schematic with point to point wiring on a perf board and placed it in a small project box from Radio Shack. Total cost less than $20.00. Talk about a savings!!
CT-17 Manual with schematic

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