Ooops.... mine are 45CT3 not 4.

I don't have a TTL module, so I usually use it in manual or automatic mode. My cable is just a straight PC socket type. I can actually use mine with anything from F100 to D200 (digital). I measured the sync voltage and it was something like 4 volts. Later, I confirmed with Metz tech support that it IS safe.

Be careful with yours because as far as voltages are concerned, the number in CTn matters. Some are really high voltage.

Metz tech support is pretty good. Someone will respond to your e-mail inquiry fairly quickly with complete information.