This portable unit adds more versatility to the Altair E-200 series intercom system as it allows call recognition in noisy and complex environments. The unit is remotely powered like the belt-type mobile units and has an additional connector to link other extensions to the line. As with the rest of the system, it includes a powerful audio buzzer with on/off selector from the front panel as well as a remote shut-off function from the main unit or a sound signal muting function for use in quiet environments.