IP-PBX vs EPABX: What FXS and FXO Gateways Do and Which Office Phone System to Buy
Quick answer: A traditional EPABX connects ordinary desk phones and outside landlines in one office using fixed hardware. An IP-PBX does the same job over your network and can use IP phones and softphones. FXS gateways let your old analog phones connect to an IP system, and FXO gateways bring outside landlines into an IP system. Choose a classic EPABX for a simple, small office; choose an IP-PBX with gateways when you have several sites, want to keep existing phones, or plan to move to IP telephony gradually.
Many buyers see words like FXS, FXO and IP-PBX in a product list and do not know which they need. This guide explains each in plain language and gives a simple way to decide.
EPABX vs IP-PBX: the basic difference
| Point | EPABX (classic intercom/PAX) | IP-PBX |
|---|---|---|
| Phones used | Ordinary analog telephones | IP phones and softphones; analog via gateways |
| Wiring | Separate telephone cable from each extension to the box | Your LAN / network cabling |
| Best for | Small offices, shops, schools, hotels with fixed rooms | Growing offices, multi-floor or multi-site businesses |
| Outside lines | Landline lines plugged in directly | Landlines via an FXO gateway, or internet telephony lines |
| Flexibility | Limited by ports on the box | Easier to add extensions and move users |
If you only need to connect a few rooms and share a couple of landlines, a classic system is simple and dependable. Our EPABX intercom system guide explains lines and extensions in detail.
What is an FXS gateway?
FXS stands for Foreign Exchange Subscriber. An FXS port is the port you plug an analog telephone or fax into. An FXS gateway turns those analog phones into devices that can work on an IP network. Choose an FXS gateway when you want to keep existing analog phones but connect them to an IP-PBX. NavKar Systems lists gateways with different port counts, such as 8 ports, 16 ports and 32 ports. Pick a port count that matches the number of analog phones, with a few spare.
What is an FXO gateway?
FXO stands for Foreign Exchange Office. An FXO port is the port that connects to an outside landline (the telephone line from your operator). An FXO gateway brings that landline into an IP-PBX, so incoming and outgoing landline calls work through your IP system. Options include 2-port and 4-port FXO gateways. Choose the port count according to the number of landlines you have.
If you need both, there is a combined 4-port FXS + 4-port FXO gateway.
What does an IP-PBX do?
An IP-PBX is the control box for calls on your network. It sets up internal calls between extensions, sends calls out through landlines or other lines, and can provide features such as call forwarding, voicemail and auto-attendant, depending on the model. NavKar lists the IP-PBX System IP-500. Always read the product page to confirm supported extensions, lines and features.
Which setup do you need?
| Your situation | Suggested setup |
|---|---|
| Small shop or clinic, a few phones, one or two landlines | Classic EPABX intercom |
| Office with 10 to 40 phones, one building | A larger EPABX, such as the 424 or 8x48 models, or an IP-PBX |
| Want to keep analog phones but move to IP | IP-PBX + FXS gateway |
| Want to keep landlines with an IP-PBX | IP-PBX + FXO gateway |
| Several branch offices | IP-PBX at each site, linked over the internet or a private network |
| Need announcements in a school, factory or hospital | See the IP paging gateway |
Planning checklist
- Count the extensions you need today and in two years.
- Count outside landlines or internet lines.
- Decide whether you will keep analog phones or buy IP phones.
- Check your network: switches, cabling and power for IP phones.
- Plan features: auto-attendant, call recording, voicemail, paging.
- Plan who will configure and support the system.
Common mistakes to avoid
- Buying an FXO gateway when you need FXS, or the other way round.
- Choosing too few ports with no room to grow.
- Running IP telephony on a weak or overloaded network.
- Forgetting power backup for the PBX and network equipment.
- Skipping a plan for who manages settings and users.
Frequently asked questions
What is the difference between FXS and FXO?
FXS connects to a telephone or fax machine inside your office. FXO connects to the outside telephone line. They are opposite ends of a connection.
Can I use my old telephones with an IP-PBX?
Yes, with an FXS gateway. Each analog phone plugs into a port on the gateway.
Do I still need landlines if I use an IP-PBX?
Not necessarily. You can use landlines through an FXO gateway, or other types of lines supported by your system. The right choice depends on your service provider and needs.
How do I know how many ports I need?
Count the analog phones (for FXS) or landlines (for FXO), then add spare ports for growth.
Shop EPABX and Intercom Systems at NavKar Systems
Not sure which system suits your office? Share your phone and line count on our bulk enquiry page.
