The ClearCom SB-704 is a unique main station not offered by any other manufacturer. It is a 4-channel Switchboard Main Station with a built-in 2-amp power supply and is rack mountable (2RU). The SB-704 includes all of the features of the MS-704, with a 4 x10 assignment matrix in place of the internal speaker (external speaker required for station monitoring). The matrix allows assignment of any of the ten intercom lines to any of the four intercom channels, to an isolated separate party-line, or to an off position.  This offers extraordinary versatility for any intercom system.