Grandstream GXW4501 E1/T1/J1 Digital VoIP Gateway

The Grandstream GXW4501 is a digital VoIP gateway with one software-configurable E1/T1/J1 span, converting up to 30 concurrent calls between digital ISDN trunks and SIP.

This is bridge equipment for a migration in progress. A business with a legacy PBX still speaking ISDN — or an ISDN30 circuit that has not been switched off yet — puts this between the old world and the new. The digital span goes in one side, SIP comes out the other, and the two systems carry each other's calls while the migration finishes on your schedule rather than a cutover weekend.

With the UK's ISDN switch-off, that job now runs in both directions: it lets an old PBX use new SIP trunks after the circuit is ceased, and it lets a new SIP platform reach an old PBX that is not ready to be replaced. Either way, one span at 30 channels is the small-site size; the GXW4502 and GXW4504 carry two and four spans.

Key features

• 1 × E1/T1/J1 span, software configurable — no hardware change between standards
• Up to 30 concurrent calls — a full E1's worth of channels
• Digital-to-SIP in both directions — old PBX to new trunks, or new platform to old PBX
• Gigabit Ethernet with integrated NAT router — sits inline where needed
• TLS and SRTP — the SIP side is encrypted even though the ISDN side never was
• Remote provisioning and management — administered without a site visit

Works with

• Grandstream GXW4502 — two spans, 60 calls
• Grandstream GXW4504 — four spans, 120 calls
• Grandstream UCM6304A — the SIP platform on the new side
• Grandstream HT881 — the analogue equivalent, for POTS lines rather than ISDN
• All Grandstream gateways

Frequently asked questions

Which direction does it convert?

Both. It presents SIP to the IP side and E1/T1/J1 to the digital side, so it serves an old PBX using new SIP trunks just as well as a new platform reaching an old PBX.

E1, T1 or J1 — which do I have?

In the UK, E1 — 30 channels, which is where the 30-call figure comes from. The span is software configurable, so the same box covers all three standards without different hardware.

Is this a long-term or interim purchase?

Usually interim — it exists to decouple the PBX replacement from the trunk migration so neither forces the other's timetable. Interim in telecoms often means years, and the box is built accordingly.

How many gateways do I need?

Count the spans, not the sites. One E1 span is 30 channels — this unit. Two spans, the GXW4502; four, the GXW4504.

Does it work with non-Grandstream PBXs?

Yes — both sides are standards-based. The digital side speaks E1/T1/J1 signalling and the IP side speaks SIP, so the vendor on either end is not a constraint in most installs. Tell us what you have and we will confirm.

Planning around the ISDN switch-off? Call 0333 242 1314 or email sales@clisecure.com and we will map the migration so nothing gets cut off before its replacement works.