For admins

A phone system or gateway

Your own phone system (like a Grandstream UCM) or a gateway for landlines can sign in to Linx, the same way a desk phone does. Linx then sends calls out through its landlines, and its calls ring in Linx.

In Linx

  1. Phone lines → + Add → Guide me → A phone system or gateway (signs in to Linx).
  2. Name it, like UCM landlines.
  3. Add the landline numbers and which extension each rings. Calls for any other number ring one extension: a landline often sends no number, and its calls ring there.
  4. Choose whether outside calls go out through it (Yes, as the main line).
  5. Create and confirm it’s you. Linx shows the server, port 5061, TLS, a username and a password, once, and How to enter this on your system.

On the phone system

Add a trunk that registers to Linx, with exactly those details: the server with port 5061, transport TLS, the username (also as its Auth ID) and the password. Set encrypted audio (SRTP) to required.

On a Grandstream UCM: Extension/Trunk → VoIP Trunks → Add SIP Trunk, type Register SIP Trunk. Linx’s page shows each setting.

Signed in

Linx’s page turns from Waiting for it to sign in… to Signed in within a minute, by itself. Then:

  • on the phone system, send the trunk’s calls to the landlines, and the landlines’ calls to the trunk;
  • call the landline from your mobile: your browser rings;
  • call your mobile from the browser.

Some extensions can call out and others can’t

A phone system or gateway usually decides what a call may do from the caller ID it arrives with, and Linx’s caller ID is not the same for everybody:

  • a person whose own number is one of this line’s numbers calls out as that number;
  • everybody else calls out as the line’s Caller ID shown to others (System → Phone lines → the line → Edit), and when that is empty, as their extension number (201, 202…).

So a gateway set to accept only one of those lets some people out and tells the others they aren’t allowed — in its own words, down the line, which sounds exactly like Linx refusing the call. It isn’t: Linx’s own check is the call permission level, and when that refuses a call you hear “This phone isn’t allowed to call that number” and the call appears in Calls as not permitted. A refusal from the gateway shows up as no answer instead.

Two ways to fix it, and the first is simpler:

  1. Set the line’s Caller ID shown to others to one of the line’s own numbers, written exactly as the gateway expects it — +97142340100 and 042340100 are the same number to a person and two different patterns to a gateway. Then everybody calls out as that number.
  2. Or widen the gateway’s own rule (on a Grandstream UCM: the outbound route’s Source Caller ID Pattern) to accept your extension numbers as well, and give the route from Linx the privilege that route needs.

When a caller hangs up on a landline

A landline never tells the gateway that the other person hung up: their exchange plays a busy tone instead. Linx listens for that tone on a phone system’s or gateway’s line and hangs up within a few seconds, so the landline is free again, and a voicemail ends there without the tone. This needs the line’s audio to be G.711 (PCMA or PCMU, what landlines use).