When replacing an EST3 with an EST4, can the existing backbox and wiring be reused?

Yes, EST4 is designed for backward compatibility with EST3 infrastructure. You can reuse existing 3-CAB series backboxes and most field wiring, including network cabling and device loops (Page 5, 10) [1].

Existing network cabling is reusable, and EST4 can support network data, audio, and telephone over a single twisted pair that previously only supported data (Page 5) [1].

Additionally, all Signature Series devices and Genesis notification appliances are fully supported without requiring rewiring (Page 5) [1].

For the user interface, the 4-3LCD display is specifically designed to mount into EST3 enclosures to facilitate these retrofits (Page 14) [1].