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Signal Tower

Signal Tower

A signal tower is a small column of coloured lights, usually also with a buzzer.

It is useful to have when running longer operations on Rose Engine Butler as it shows at a glance the system’s current status (e.g., is it still running or not). And they LED lights are typically bright enough that they can be seen from across the shop.

Rose Engine Butler is also configured to illuminate the red light if a typical error is encountered.

The presence of a buzzer is useful as it can alert you if you are not looking in that direction. This is especially useful if an error is encountered.

Use of a signal tower is optional: everything works without one.

What It Tells You

Signal	What it means
Red Light	Something went wrong and your attention to the system is needed: an axis had a following error, a limit switch tripped, or the Base Box or Expansion Box lost contact with the Raspberry Pi (see Lost contact). This lamp stays lit until you resolve the error and re-power on Rose Engine Butler.
Green Light	The machine is working on a task which could be lengthy. These are the operations setup to illuminate the green light: a spindle is turning, an indexing move, a synchronized movement, a threading movement, an MDI command is running, or a Gcode program is running. Other activities (e.g., jogging) do not illuminate this light.
Siren	A siren which is used to alert you to certain conditions are achieved: A condition is triggered which illuminates the red light → 3-second siren sounds Tasks outlined which trigger the green light to illuminate are completed → 3 short beeps Gcode program encounters an M0 or M1 (Pause) command → 2 short beeps
Both lights off	The machine is idle, finished, or turned off.

The full list of what does, and does not, turn each light on is in Inputs, Outputs, and Sounds - Signal Tower. The buzzer's sounds are explained in Sounds.

Why It Is Useful

• Long programs. A rose engine pattern can run for hours. This enables you to work elsewhere in the shop and see from a distance whether the machine is still running (green), has finished (dark), or has stopped with a problem (red).
• Hear it, even when you can't see it. The buzzer tells you the moment something goes wrong, or when a job is done, without watching the screen.
• Problems stay visible. A following error, a tripped limit switch or a lost connection to a box can be over in an instant. The red light stays on so you know it happened, even if you were not there to see it.

What to Buy

The signal tower must be:

Signal towers sold for machine tools (often listed as "LED stack light" or "tower light 24V with buzzer") meet these requirements.