Thanks for your reply. The manual describes the control cable as a monaural cable with mini plugs (no resistance). The manual describe "control devices that are compatible with the "SR" logo mark" but does not go into any further depth.

There is an RSC232c input. In the index it is described as D-sub 9 pin combination in/out mini DIN 6pin (x2)and is a control plug. This would probably accept the plug directly however another section of the manual states:
"DO NOT MAKE ANY CONNECTIONS TO THIS TERMINAL. This terminal is used in the factory setup." Which makes me concerned about using it.

Any suggestions are welcome.

Thanks again,

Ralph