The 152 Switchboard series enables audio and video door entry systems to be set up either with sound system or AC call tones.
These switchboards have two operating modes: "Internal" and "External":
In "Internal" mode, calls and conversations with privacy are between the switchboard and individual interphones and between the switchboard and an external entrance panel.
In "External" mode, calls and conversations are directly between individual interphones and the external entrance panel.
The line selection keys, which provide communication between interphones and the switchboard, are supplied with luminous indicators as well as an associated acoustic signal to enable the user to locate the calling interphone.