Pioneer AVIC-S2 - Manual (Page 16)

1.8 Attaching and Detaching the Device
To attach the unit to the holder and bracket, insert the unit into the holder bottom
first and then press firmly at the top, near the Pioneer logo. The unit should lock
securely into the holder.
Press down on the lever at the top of the holder to release and detach the unit.
Please hold the unit securely while detaching to avoid damage.
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