Very few organisations move to IP telephony in one step. There is the fax machine in accounts, the analogue phones in the lift and the car park, the PRI the carrier will not switch off until next year, and the branch that still needs a local line. VoIP gateways are what let a modern IP PBX such as 3CX carry on working with all of that. Dinstar makes a wide range of them, and this article explains what each type does and how to choose.
Three kinds of gateway
FXS gateways provide analogue ports that behave like a line from the telephone company. You plug in an analogue phone, a fax machine, a door phone or a paging amplifier, and the gateway registers each port to the IP PBX as an extension. Dinstar’s FXS range runs from 4 ports for a small office to high-density units for hotels and campuses with hundreds of analogue handsets.
FXO gateways do the opposite: they connect to analogue lines from the carrier and present them to the IP PBX as trunks. They are used where SIP trunks are not available, where a legacy line must be kept for a specific number, or as a fallback path if the internet fails.
Digital gateways connect ISDN PRI (E1/T1) or BRI circuits to a SIP system. They are the bridge for enterprises with a carrier PRI, and for connecting an old digital PBX to a new IP PBX during a phased migration so that both systems can call each other.
Where they fit in practice
- Hotels – hundreds of analogue guest-room phones kept in service on a new IP PBX with high-density FXS gateways, avoiding the cost of replacing every handset.
- Offices with a PRI – a digital gateway connects the carrier’s E1 to 3CX or another SIP PBX while the SIP trunk is provisioned and numbers are ported.
- Fax and alarm lines – an FXS port with T.38 support keeps a fax machine or an alarm panel working across an IP network.
- Remote sites – a small FXO gateway gives a branch a local emergency line and a fallback if the WAN goes down.
Sizing and specification
Count ports, not phones. For FXS, count every analogue device including fax, door entry and paging. For FXO and digital, count the lines or channels you need to keep, and leave headroom for a migration period when both old and new paths are in use. Check codec support (G.711 for quality, G.729 for bandwidth), T.38 for fax, and whether you need the gateway to survive a PBX outage by routing calls locally.
Configuration notes
Dinstar gateways are configured through a web interface, and templates exist for the common PBX platforms. The important settings are the SIP registration details, the dial plan (which prefixes go out via which port), caller ID handling and the echo cancellation and gain settings on analogue ports. A gateway that sounds bad is almost always a gain setting, not a fault.
Why Dinstar
Dinstar has been building gateways for two decades and its range covers every port count from 1 to several hundred. The units are interoperable with the major IP PBX platforms, firmware is maintained, and the price point is realistic for the mid-market. For Zen customers there is a further advantage: the gateway, the PBX and the handsets come from one distributor, so compatibility questions are answered once.
Getting it right
Zen Interactive Technologies distributes Dinstar in the UAE and GCC and stocks the popular FXS, FXO and digital models in Dubai. Tell us what you need to connect and to which PBX, and we will recommend the model and port count. The range is on the Dinstar page, and datasheets are attached to each product.