Grandstream HT881 Analog FXO Gateways

The Grandstream HT881 is an eight-port analogue FXO gateway — the larger sibling of the HT841. It connects eight real telephone lines to a SIP platform, so an IP phone system can make and receive calls on lines that predate it.

FXO and FXS are opposites, and mixing them up is the classic ordering error. An FXO port plugs into a line; an FXS port plugs into a phone or fax. To keep eight existing lines while moving the handsets to IP, this is the right unit. To keep old analogue handsets or faxes working on a VoIP system, you want an FXS gateway such as the HT818.

Eight ports means eight simultaneous calls, not eight numbers. That is the sizing question people get wrong. A business with twelve lines that never has more than five calls at once needs fewer ports than it thinks; a business with four lines that are all busy at 9am needs every one. Count the busiest hour.

Key features

• 8 FXO ports — eight analogue lines, eight simultaneous PSTN calls
• 1 FXS port — for a fax machine or a single analogue phone
• 3 SIP profiles — register to more than one platform or provider
• Lifeline support — PSTN calls keep working through a power or internet failure
• Failover SIP server — a second server takes over if the primary is unreachable
• T.38 fax over IP — the protocol that makes fax survive an IP network
• Built-in NAT router — two Ethernet ports, so it can sit inline if needed
• Encryption and secure automated provisioning — deployable at volume

Works with

• Grandstream HT841 — the same gateway with four FXO ports
• Grandstream GXW4108 — the earlier eight-port FXO gateway this replaces
• Grandstream HT818 — the FXS equivalent, for connecting analogue phones and faxes
• Grandstream HT813 — one FXS and one FXO in a single small unit
• Grandstream UCM6304 IP PBX — a platform to register it to
• All Grandstream gateways

Frequently asked questions

FXO or FXS — which do I need?

FXO connects to a line; FXS connects to a phone or fax. Keeping existing telephone lines on a new IP system needs FXO, which is this. Keeping old handsets or faxes working needs FXS — the HT818.

How many ports do I actually need?

One per simultaneous call, not one per line you own. Look at the busiest hour of the week: if twelve lines never carry more than five calls at once, eight ports is generous.

What does lifeline support do?

It falls back to a direct connection between the FXS port and a PSTN line when power or internet fails, so a phone plugged into it still gets dial tone — which is why FXO gateways remain in care homes, lifts and alarm installations.

Will fax work through it?

It supports T.38 fax over IP. Fax over any IP network remains fussy, so test with the actual machine before committing to the design.

How is it different from the GXW4108?

The HT881 replaces it with a richer feature set — same eight-port FXO idea, more SIP profiles, better provisioning and current firmware support.

Can it register to two providers at once?

Yes — three SIP profiles, plus a failover SIP server if the primary becomes unreachable.

Migrating a block of analogue lines to SIP? Call 0333 242 1314 or email sales@clisecure.com and we will size the ports against your actual call volume.