If your premises has no fixed telephone line — or the one you have is expensive to install and slow to repair — a GSM PABX solves both problems at once. The MS108-GSM puts a SIM card trunk, one PSTN line and eight extensions in a single unit, so ordinary analog phones on desks ring through a mobile network instead of copper.

It is the practical answer for small offices, shops, workshops and home offices where fixed lines are unavailable, unreliable or overpriced.

What a GSM PABX actually does

A PABX gives a site internal extensions and shared access to outside lines. A GSM PABX replaces — or supplements — the outside line with a mobile trunk:

• Built-in GSM module accepts a standard SIM card and uses it as a trunk line
• PSTN and GSM run simultaneously — one CO line and one GSM trunk are available at the same time
• Least-cost routing (LCR) decides which trunk carries each call, so traffic goes out over whichever line is cheaper
• Eight extension ports connect ordinary analog telephones — no IP phones, no network switch, no software licences

There is no IP-PBX behind this box and no cloud subscription in front of it: plug in phones, insert a SIM, and the site has a working phone system.

GSM PABX vs GSM VoIP gateway — the distinction that matters

These two product types get confused constantly, and choosing the wrong one wastes money:

Short version: a GSM gateway feeds an IP-PBX; a GSM PABX replaces the need for one. If your people have desk phones and no network infrastructure, the PABX fits. If you already run an IP-PBX and want mobile calls flowing into it, choose a gateway instead.

Features that matter in daily use

Answer calls professionally. Operator mode or auto-attendant, with DISA in three 20-second segments and outgoing messages (OGM) recorded from a telephone or downloaded from a PC. Callers hear a greeting and dial the extension they want, without a receptionist.

Never miss a call. Incoming calls can forward automatically to a mobile phone, alongside call forward, call transfer, call pickup and call barge-in.

Control cost. Least-cost routing across PSTN and GSM, call restriction by class assignment, extension dynamic lock, multiple dial-out modes and CO line groups — you decide which extensions may call which networks.

Everyday conveniences. Caller ID on external, intercom and transferred calls, abbreviated dialling, extension number query, flexible extension coding, internal hotline, Do Not Disturb, three-party conference and group call.

Building access. Door phone and door opener support lets any extension answer the door station and release the door — often replacing a separate intercom purchase.

Where the MS108-GSM fits best

• Offices without a fixed line — new builds, serviced offices and converted spaces with high carrier quotes or long lead times
• Small shops and clinics — eight extensions plus a door phone cover a counter, a back office and a consulting room
• Workshops and warehouses — a phone system where cabling was never installed
• Home offices and annex buildings — proper extensions, not a single cordless handset
• Temporary and seasonal sites — pop-up shops, site offices and events where the phone system moves with the site
• Resilience — keep the PSTN line and add a GSM trunk so calls survive a fixed-line failure

Specifications at a glance

FAQ

Q1. What is a GSM PABX? A PBX with a built-in GSM module that uses a SIM card as an outside trunk, so a site can call and be called over a mobile network instead of — or alongside — a fixed line. The MS108-GSM adds one PSTN line and eight extension ports.

Q2. Do I need internet or an IP-PBX? No. It is standalone: analog phones plug into the extension ports, the SIM provides the outside line, and the built-in software handles routing.

Q3. Can a fixed line and the SIM work at the same time? Yes. Both trunks are available simultaneously, with least-cost routing choosing the cheaper path per call and line groups controlling which extensions use which trunk.

Q4. How is this different from a GoIP GSM gateway? A GoIP gateway has no extension ports and must register to an IP-PBX or VoIP platform. The MS108-GSM has eight analog extension ports and provides the entire phone system itself.

Q5. What happens when nobody is at the desk? Incoming calls can forward automatically to a mobile phone, the auto-attendant can route callers to the right extension, and DND is available per extension.

Q6. Can it control a door lock? Yes — door phone and door opener functions let an extension answer the door station and release the door.

The bottom line

A GSM PABX turns a SIM card into a real phone system: eight extensions, one PSTN line, least-cost routing between them, and the everyday features — auto-attendant, transfer, conference, call restriction, door phone — that let a small site sound bigger than it is.

If the site has no network infrastructure and no fixed line, the MS108-GSM is the shortest path to working extensions. If you already run an IP-PBX and want mobile calls entering it, choose a GSM VoIP gateway instead — and tell us what is on site, because the two are often used together in the same building.