3CX Integration · Communications Infrastructure

Bridge analog lines and E1/PRI trunks with a 3CX voice gateway

A voice gateway bridges legacy analog PSTN lines, fax machines and E1/PRI trunks into 3CX over SIP — so you can move to modern communications without abandoning the lines and devices you can’t replace yet.

As a Fanvil Platinum Partner, ECOLOR selects the right gateway (FXO, FXS or E1/PRI), configures it, and registers it to 3CX as a SIP trunk or extension.

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FXO / FXS / E1-PRI
Keep analog & fax
Bridge legacy to 3CX

What is a 3CX voice gateway?

A 3CX voice gateway (also called a VoIP gateway) is a device that bridges legacy telephony into the 3CX phone system over SIP. The gateway converts analog lines or legacy digital trunks into SIP calls that 3CX understands, then registers itself to 3CX as either a SIP trunk or an extension.

This lets a business keep its existing analog lines or E1/PRI trunks while moving to 3CX — or migrate off them gradually without cutting service. Your phone numbers, fax machines and essential lines keep working while you gain the modern features of 3CX.

The gateway type depends on what you need to connect. An FXO gateway brings analog PSTN lines into 3CX; an FXS gateway connects analog devices such as phones, fax machines and door/elevator phones; and an E1/PRI (or ISDN BRI) gateway connects legacy digital trunks. Common gateway vendors include Fanvil, Patton and Grandstream.

FXO — connects analog PSTN lines into 3CX
FXS — connects analog devices (phones, fax, door/elevator) to 3CX
E1/PRI and ISDN BRI — connect legacy digital trunks
The gateway registers to 3CX as a SIP trunk or as an extension

What a voice gateway connects to 3CX

FXO — PSTN lines

Brings analog phone lines from your carrier (STC and others) into 3CX as a SIP trunk for inbound and outbound calls.

FXS — analog & fax

Connects analog devices that can’t go IP — fax machines, door and elevator phones, analog handsets — so 3CX treats them as extensions.

E1/PRI trunks

Bridges a legacy E1/PRI digital trunk (30 channels) into 3CX as a SIP trunk, preserving your line capacity during migration.

ISDN bridging

Connects legacy ISDN BRI trunks to 3CX through a BRI gateway registered as a SIP trunk.

Fanvil / Patton gateways

We work with Fanvil (as a Platinum Partner), Patton and Grandstream gateways, choosing the model that fits your port count.

SIP registration to 3CX

The gateway is configured to register to 3CX over SIP, with inbound and outbound routing and dial plans set correctly.

Which gateway do you need?

You have	Gateway type	Connects to 3CX as
Analog PSTN lines	FXO	SIP trunk
Analog phones / fax / door phones	FXS	Extensions
E1/PRI digital trunk	E1/PRI gateway	SIP trunk
ISDN BRI	BRI gateway	SIP trunk

The number of ports you need depends on how many lines or devices run simultaneously — we help you size it correctly.

How ECOLOR integrates a gateway

Survey your lines/devices
We inventory your analog lines, digital trunks and devices (fax, elevator, door phones) to decide what must be connected and kept.
Select the gateway
We choose the gateway type (FXO / FXS / E1-PRI), model and port count that match your call volume.
Configure & register to 3CX
We configure the gateway and register it to 3CX over SIP as a trunk or extension, with codec and security settings.
Route inbound/outbound
We set routing rules and dial plans for inbound and outbound calls across the gateway.
Test & hand over
We test calls, fax and both directions, then hand over the system with documentation and support.

Gateway bridging

Analog / PSTN / E1-PRI linesVoice gateway (FXO/FXS/PRI)SIP registration3CX phone system

What you need

Inventory of analog lines / devices / trunks
Gateway sized to port count
3CX reachable for SIP registration
Carrier details (STC or other) for the lines or trunk

Missing some of these? We handle the inventory and sizing as part of the consultation.

Saudi deployment notes & limits

Some devices simply can’t go IP — fax machines and elevator/door phones are common examples. An FXS gateway lets you keep these essential analog devices and connect them to 3CX as extensions, without replacing them.

If you run an E1/PRI digital trunk, you can migrate to SIP gradually: the gateway bridges your current trunk into 3CX now, then you shift load to a SIP trunk over time without cutting service or losing your numbers.

We integrate Saudi PSTN/STC lines with 3CX through FXO gateways, accounting for local codecs and signalling. A gateway’s natural limit is its port count, so we size it based on your real simultaneous-call volume rather than nominal line totals.

Frequently asked questions

Can I keep my analog phone lines with 3CX?

Yes, via an FXO gateway. It brings your analog PSTN lines into 3CX where they appear as a SIP trunk, so your inbound and outbound calls continue on the same lines.

Can I keep fax machines / door phones?

Yes, via an FXS gateway. It connects analog devices such as fax machines, elevator and door phones to 3CX, where they are treated as extensions — no replacement needed.

Can 3CX connect to an E1/PRI trunk?

Yes, via an E1/PRI (PRI) gateway. It bridges the digital trunk into 3CX as a SIP trunk, preserving your capacity while you migrate toward SIP.

Which gateway brands do you use?

We work with Fanvil (as a Platinum Partner), Patton and Grandstream, selecting the model that fits your connection type and port count.

Does the gateway connect as a SIP trunk or extension?

It depends on the type. FXO, E1/PRI and BRI gateways connect as SIP trunks, while FXS gateways connect as extensions — one per analog device.

Can I migrate off E1/PRI gradually?

Yes. The gateway bridges your current trunk now, then you move load to a SIP trunk in phases without cutting service or losing your numbers.

Bridge legacy lines to 3CX with ECOLOR

Keep your analog lines, fax machines and E1/PRI trunks while you move to 3CX — or migrate off them gradually. We select the right gateway, configure it, register it to 3CX and hand it over ready to use.