Clifford 515U is compatible with:

• Clifford Concept 300
• Concept 500
• Concept 600
• Concept 650
• Concept 650MKII
• Avantguard 5.5
  

The picture is for illustration only, this unit is a new updated version of the G4 unit, current model sold with all new Clifford alarms. It has 4 wire input and very easy to install.

G4 tell tale sirens of siren replacement was loss of Arm and Disarm chirps. If this has happened to your system, your battery back-up no longer works and a new siren will cure this.