My SP is in a rack mount and I don’t have access to the three CV jacks. I want to run 3’ patch cables to the front permanently so I can use them with my CP-251, now and then. But, when I plug in my patch cable (with nothing on the opposite end), no sound comes out of the SP. Evidently, if a patch cable is plugged into a CV jack, it has to be connected to the CP-251 on the other end. What do I need at the other end of the patch cable to simulate it not being plugged in? Thanks. Jim
A dummy plug perhaps? 
A dummy plug is a plug with no cable on the end, with the sleeve and tip shorted to each other.
Thanks. I tried shorting the ends of the cable and the shorted cable still prevents sound from coming from the SP. It must require a voltage level?
Maybe. Are you using TS or TRS cables?
I’m using TS cables. It occurred to me that shorting tip - sleeve might not work, but I’m not sure what to short in a TRS to get this to work. Any idea?
Try using TRS cables. That may eliminate the problem. If not, do NOT plug into the Volume CV. That will silence the SP, unless a voltage is going through it. You may get a result by shorting the ring to tip, however. 
Exactly right voltor07! It’s only the VOL CV that silences it - shorting ring to tip brings it back. Thanks! Jim
Glad I could help! 
Hey,
Just thought I would post this thread link here, it explains my Phatty/patchbay/dummy plug setup in some detail:
http://forum.moogmusic.com/viewtopic.php?f=7&t=14648
Regards,
David Smyth
NZ