CU100 Central Unit It is the main controller with 4 trunks, each powering a wired Chairman and wired Delegates with a total 15 sets. It also has abalanced line output for connection to external sound system and recording device. External audio source such as from PC or DVD audio ( or other audio source ) are available for feed to the delegate units. CM100 is Chairman unit which has control over other delegates ie. higher priority talk and cancel feature. It comes with 2 m extension cable for connectivity to the next delegate unit, built in speaker with volume controller and illuminated gooseneck microphone. DM100 is Delegate unit comes with 2 m extension cable for connectivity to the next delegate unit, built in speaker with volume controller and illuminated gooseneck microphone. Product of MALAYSIA.