Machine signaling has a vocabulary, and Schneider's Harmony range organizes it into three families that answer three different questions: the XVS voice alarm when the operator must be told what happened, the XVB/XVM tower lights when the machine must show its state at a glance, and the XB4/XB6 pilot devices when a single honest point of light or a pushbutton is the whole message. Choosing by urgency and distance — not by catalog order — is what makes a signaling system work.
XVS: the voice that says what and where
Tower lights say something is wrong; voice alarms say what is wrong. The XVS family plays configurable messages — "hydraulic level low, station 3" — through field-mounted sounders, cutting diagnosis time on multi-machine floors to the length of one sentence. Noisy plants are its natural home: a voice cutting through broadband noise beats another colored lens.
XVB/XVM tower lights: the state at a glance
The tower-light family — LED steady and flashing tiers in the XVB range, the modular XVM builds — encodes machine state in the classic red/amber/green grammar, visible down an aisle. A pre-wired LED unit like the Schneider XVMB2RSB 45 mm tower light shows how far the category has industrialized: pole-mounted, 24 V, ready to signal. Tower lights answer "is it running, idle or faulted" from across the hall — and answer nothing beyond that.
XB4/XB6: the point of contact
Pilot lights and pushbuttons close the loop at arm's length: the XB4 and XB6 families put start, stop, and confirmation where the operator's hands are, and a single indicator where the eyes already are. They carry no status story — that is the tower's job — but nothing else beats them for the local sentence "pressed, powered, interlocked."
The decision rule
Urgency with explanation: XVS voice. State at distance: XVB/XVM towers. Confirmation at the panel: XB4/XB6. Real plants layer all three — voice for the what, tower for the where, pilots for the who — and wire them into the same controller I/O so the vocabulary stays consistent.
Can the XVS play my own messages?
Yes — configurable audio libraries are the point. The discipline is keeping messages short, specific and numbered, so the voice is a diagnosis, not a radio station.
LED tower lights — steady or flashing?
Steady for state, flashing for demand: the grammar works only if the plant agrees on it once and never improvises. Document the vocabulary on the panel drawing, not in folklore.
