For those cases where a more pleasant tone is desired, instead of the whistle within the control panel of the >DA-500 or DA-600, the DA-655 provides a pleasant tone. This unit can be hardwired to the control panel of the Mier DA-500 or Mier DA-600, and emits a chime when a vehicle is detected. There is also a volume control, and this unit can be turned up to a high level.