[Ether]

Originally Posted by Hugh Meyer

http://www.chiefdelphi.com/forums/sh...ghlight=victor

Thanks for the link, Hugh.

In that thread, Don Rotolo posted:

Originally Posted by DonRotolo

you can use a 5.1 volt Zener diode (and a low-value series resistor) to clamp the input voltage to 5 volts or so.

Like this? That seems to me to be the safest way to proceed, since my concern is to make sure I do not damage the Victor:

• As long as the zener doesn't burn up, it protects the Vic by limiting the positive voltage to +5 volts applied at the Vic's input
  
  
• The zener also limits the negative voltage applied to the Vic input to approx -0.7 volts instead of -12V (as Eric suggested)
  
  
• The value of resistor R1 becomes less critical. It just needs to be large enough to prevent the zener from burning out, and small enough to assure that the voltage drop across it doesn't drop the Vic input voltage below 5 volts. Since Hugh indicated that 1200 ohms series resistance worked well with an 8-volt supply, I'm guesstimating maybe 1800 ohms for R1 would be a good choice for my 12 volt signal?