I built a phone system because no one answers me

A DIY phone system built around 3CX is turning “nobody answers” into instant, reliable communication—inside the house, across the business, and even into home automation and a local AI voice assistant. The core move is replacing scattered cell phones and silent Apple Watch notifications with a managed VoIP setup that can ring specific people, run menus (IVR), and bridge legacy analog wall phones into modern SIP calling.

The project starts with a practical frustration: calls to family members routinely go unanswered because phones are missing, muted, or ignored. Instead of relying on mobile carriers and individual devices, the setup installs 3CX so multiple family members can share a single phone system. For speed, the cloud route is used first: sign up for the 3CX SMB plan, get a hosted phone number, and register “soft phones” through the 3CX app using QR-code provisioning. User accounts are then created for the daughters, assigning them extensions and numbers so internal calls work immediately.

To connect physical phones to a cloud-hosted 3CX instance, the system needs a bridge inside the local network. The solution demonstrated is a Raspberry Pi running 3CX’s SBC (session border controller) software. The Pi is prepared by flashing Raspberry Pi OS Lite onto a microSD card, preconfiguring Wi‑Fi/credentials, enabling SSH, and then provisioning the SBC from the 3CX admin portal. Once the SBC is online and registered, local phones can authenticate through it and reach the cloud-hosted 3CX system.

The build then goes further than typical VoIP installs by supporting “retro” analog wall phones from TV-era aesthetics. Those phones use POTS (plain old telephone service) with RJ11 cabling and analog signaling, while modern 3CX calling uses SIP (session initiation protocol) over IP. The workaround is an analog telephone adapter (ATA) from Grandstream (HT801). The ATA translates between analog handset signaling and SIP, registers with 3CX via the Raspberry Pi SBC, and allows the old phones to place and receive calls as if they were modern extensions.

For calls outside the home or business, the system adds a SIP trunk—effectively a tunnel between 3CX and a phone-number provider. A DID number is purchased through VoIP.ms, then routing and trunk credentials are configured in 3CX so inbound calls reach the right internal destinations and outbound dialing works with the chosen prefix/strip rules. To avoid every call ringing every phone, a digital receptionist/IVR is configured: callers dial a virtual extension, hear a menu prompt (“press one,” “press two,” etc.), and are routed to specific extensions or ring groups.

The most distinctive payoff is calling a local AI and controlling smart home functions from an analog handset. Using Home Assistant, the setup integrates voice control so the ATA can auto-dial the Home Assistant endpoint (or route via an on-prem SIP trunk). After configuring the Grandstream HT801 codec settings (Opus) and Home Assistant’s VoIP integration to use a specific assistant (Terry), the phone becomes a voice interface for automation—turning lights on/off, querying server room temperature, and triggering other actions through webhooks. The result is a single, nerdy communication hub that finally makes family and business calls answerable—and programmable.