The Park Alarm is a reversing aid to help prevent this situation. They turn on when you select reverse gear, and lets you know when you're getting close by audible (TA03), and visual signaling (TA04)Tech Info

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Power :12 volt DC

Dimensions...
TA03 - Main unit - W : 69mm / H : 21mm / L : 109mm
- Buzzer - W : 50mm / H : 18mm / L : 75mm

Ta04 - Main unit - W : 72mm / H : 23mm / L : 110mm
- Readout - W : 90mm / H : 21mm / L : 32mm