The MCS 563 L system unit consists of a terminal board for the connection of loudspeaker, up to three buttons, microphone, priority and clear button and two LED’s for microphone on (green) and request-to-talk (red). Another terminal board is available for an external gooseneck microphone and illuminated ring or any other indication of the ready-to-talk status. The customer can select the type of external operation buttons, LED’s and gooseneck microphone. Beyerdynamic recommends the use of a piezo button with integrated dual colour illuminated ring. A condenser (back electret) microphone with impedance transformer for AB-powering must be used. The equalisation has been optimised for Beyerdynamic microphones. If microphones from other manufacturers are used, the MCS 563 L must be adjusted to compensate for these microphones. The MCS 563 L can be used as a chairman’s microphone unit with three buttons or as a delegate’s microphone unit with one control button. The use depends upon the system configuration with the MCS Editor software. The ready-to-talk condition of the microphone is indicated by the red illuminated ring. In the request-to-talk mode of the discussion system the microphone button is used to activate the request. Control voltages to power external LED indicators are available on the terminal board. These indicate microphone on, when released by the operator of PC or media control system. Dual colour or individual LED indicators may be used. In the request-to talk mode of the discussion system the microphone button is used for a request to talk. If the microphone button is pressed once again the request to talk can be cleared by the delegate. If the MCS 563 L is used as a chairman’s microphone unit, a priority and clear button can also be fitted. The chairman does not depend upon the limited number of open microphones (NOM). Using the priority button the chairman can intervene into the discussion and temporarily mute or clear the activated delegate microphone units depending upon the system configuration. Using the clear button all activated delegate microphone units are switched off.