Zultys MG4 4-Port FXO Analog VoIP Gateway SIP PSTN Trunk PBX Integration Wty

Zultys MG4 4-Port FXO Analog VoIP Gateway

The Zultys MG4 is a compact 4-port FXO analog VoIP gateway that bridges existing PSTN analog phone lines to a modern SIP-based VoIP PBX — backed by a 12-month Reboot IT warranty. Retain your analog PSTN lines and existing phone numbers while migrating to VoIP, without replacing your entire phone infrastructure.

Key Benefits

• 4 x FXO Ports: Four analog PSTN line inputs allow up to four simultaneous incoming or outgoing calls through your existing phone lines via the VoIP PBX.
• PSTN-to-VoIP Bridge: Connects analog PSTN lines directly to SIP-based PBX systems — preserving existing phone numbers and PSTN lines during a VoIP migration.
• Broad PBX Compatibility: Works with Zultys MX, 3CX, Asterisk, FreePBX, and any standards-based SIP PBX — not locked to a single vendor ecosystem.
• Cost-Effective Migration: Add VoIP capability progressively while keeping PSTN as a fallback or primary trunk — no big-bang cutover required.
• Compact & Mountable: Small form factor suitable for rack or wall mounting — fits in a server room, comms cabinet, or IT closet.
• Standards-Based SIP: Uses standard SIP signalling and RTP for audio, ensuring compatibility with virtually any modern VoIP PBX or hosted SIP trunk provider.

Performance in Use

For businesses moving from traditional PSTN to VoIP, the MG4 solves the most common migration challenge: what to do with existing analog phone lines. Rather than cancelling all PSTN lines immediately, the MG4 lets you run PSTN and VoIP in parallel. Incoming calls arrive on PSTN lines, are received by the MG4, and delivered to the VoIP PBX as SIP calls, routing to IP phones throughout the office.

For businesses already on a VoIP PBX that want to retain PSTN as a backup trunk — for redundancy if the internet fails — the MG4 provides exactly that. With four simultaneous call paths, it handles the busiest periods in most SMB environments. Failover configurations can route calls to PSTN automatically if the SIP trunk or internet connection drops.

The MG4's broad SIP compatibility means it works with popular open-source PBXs like FreePBX and Asterisk as well as commercial systems including 3CX and Zultys MX. Configuration is straightforward via a web interface, and standard SIP/RTP ensures no proprietary codecs or licensing are required.

Tech Specs

FXO Ports	4 x RJ-11 analog PSTN line inputs
Simultaneous Calls	Up to 4
Protocol	SIP (RFC 3261), RTP
Network	10/100 Ethernet
PBX Compatibility	Zultys MX, 3CX, Asterisk, FreePBX, any SIP PBX
Management	Web-based interface
Form Factor	Compact, rack or wall mountable
Power	External AC adapter
Warranty	12 months — Reboot IT

Is It Right for You?

Best For ✓	Not For ✗
Businesses migrating from PSTN to VoIP	Environments with no analog PSTN lines
Retaining existing phone numbers during migration	High-call-volume contact centres (4 lines max)
PSTN failover/backup for VoIP PBX systems	Direct connection to analog handsets (FXO, not FXS)
3CX, FreePBX & Asterisk deployments	Non-SIP proprietary PBX systems

Condition Grades

Grade	Condition	Cosmetics
A — Excellent	Fully tested & working	Minimal marks or scuffs, near-new appearance
B — Good	Fully tested & working	Light wear, scratches or marks visible on chassis

Frequently Asked Questions

What is the difference between FXO and FXS ports?

FXO (Foreign Exchange Office) ports connect to PSTN lines from the telephone company — this is what the MG4 has. FXS ports connect to analog handsets or fax machines. The MG4 bridges PSTN lines to a SIP PBX; it does not connect directly to analog handsets.

What PBX systems does the MG4 work with?

The MG4 is compatible with any standards-based SIP PBX including Zultys MX, 3CX, Asterisk, FreePBX, and most hosted SIP trunk providers. It uses standard SIP/RTP so it works with virtually any modern VoIP system.

How many simultaneous calls can the MG4 handle?

Up to 4 simultaneous calls — one per FXO port. Each port corresponds to one PSTN line, so total concurrent call capacity matches the number of active PSTN lines connected.

Can I use the MG4 as a PSTN backup for my VoIP system?

Yes. Many businesses use the MG4 to provide PSTN failover — if the internet or SIP trunk fails, outbound calls can route through the PSTN lines connected to the MG4 instead.

What are the shipping costs?

Shipping costs apply based on size and destination — rates are calculated at checkout.