If I remember right, and others will chime in if incorrect I am sure
1. Connection to Head Unit
2. Connection to Window antenna
3. Connection to power
Your photo is of the antenna amplifier, which there are other posts telling to sand the area around the screw attaching to body (bad idea in my opinion) or just buy a new module to replace for around $55.00 (link below)
Pelican Parts - Product Information: OEM-98764710500
