Grandstream HT812 Analog FXS IP Gateway – 2 Port + NAT Router

The Grandstream HT812 puts two analogue phones or fax machines onto a VoIP system. This is the original HT812 — one of the most widely deployed ATAs in the world, the unit providers shipped by the pallet when analogue lines started disappearing.

Each FXS port is its own extension: plug in the analogue handset, fax machine or door phone, register the port, and the device carries on exactly as before — same dial tone, same ring — while the call travels over SIP.

The router inside is what separates the HT8xx from a bare ATA. Two Gigabit ports with NAT routing mean it can sit directly behind the broadband modem and share the connection onward, or simply hang off a spare LAN port like any other device. In a small office or home office, one box handles both jobs. A newer revision exists as the HT812 V2; the job they do is the same.

Key features

• 2 FXS ports — each an independent analogue extension with its own number if you want
• 2 × Gigabit Ethernet with NAT router — sits at the edge or on the LAN, your choice
• 2 SIP server profiles — the two ports can register to different providers
• T.38 fax relay — fax carried as data, not squeezed through a voice codec
• 3-way conferencing per port
• TLS and SRTP with AES encryption — the SIP side is protected
• Automated provisioning — TR-069 and encrypted XML configuration for fleet rollouts

Works with

• HT812 V2 — the current revision of this ATA
• HT814 — the same unit with 4 ports
• HT813 — 1 FXS + 1 FXO, when you also need to keep an analogue line
• PSU for HT812 / HT813 — spare or replacement power supply
• IP PBX solutions — register the ports to an on-site or cloud platform
• All Grandstream gateways and ATAs

Frequently asked questions

Will my existing phone just work?

Yes. An FXS port supplies line voltage, dial tone and ring current exactly like the old analogue wall socket, so the handset behaves normally. Nothing changes for the person using it.

Can the two ports have different numbers?

Yes — each port registers independently, and with two SIP profiles they can even sit on different providers. A phone on one port and a fax on the other, each with its own number, is the classic setup.

Does fax actually work?

Fax is the part worth planning. T.38 relay carries the fax as data rather than as audio, which is what makes it reliable — but your provider has to support T.38 at the other end. Ask them before you port the fax number.

What is the NAT router for?

It lets the HT812 sit directly behind the modem and share the connection to the rest of the network, so a very small site needs no separate router. If you already have a router, ignore it — the HT812 works as an ordinary LAN device too.

This or the V2?

Same job — two analogue ports onto SIP. The V2 is the newer revision; this original registers to the same platforms and is the unit to match if you already run a fleet of them.

Moving a fax, alarm or door phone off an analogue line? Call 0333 242 1314 or email sales@clisecure.com and we will check T.38 support with your provider before you order.