GSM gateway or SIP telephony: what’s the difference and which to choose for your business
Sado AI team · · 4 min read
In short
A GSM gateway is a box you put SIM cards into: it passes mobile calls to an office PBX or IP telephony. Each SIM handles one call at a time, quality depends on the mobile signal, and the box needs power and internet in the office. Many mobile operators restrict SIM use in gateways. With SIP telephony the line comes from the provider over the internet, adding channels is easy and no office equipment is needed. For a new setup SIP is usually easier; a gateway stays a stopgap.
How each one works
A GSM gateway is a box in your office with one or more SIM cards inside. A customer calls the mobile number, the call travels over the mobile network to the gateway, and the gateway hands it to the PBX or a staff member’s IP phone. Outgoing calls go the other way.
SIP telephony has no SIM cards and no box. The number is opened with a provider, and calls come from the provider over the internet straight to your system: a cloud PBX, an IP phone or an AI operator.
Comparison table
| Point | GSM gateway | SIP telephony |
|---|---|---|
| Where the line comes from | The mobile network, through a SIM card | The provider, over the internet |
| Calls at the same time | One SIM, one call; more needs more SIMs and ports | As many as your channels; the provider adds more |
| Sound quality | Depends on the mobile signal and where the box stands | Depends on internet quality |
| Office equipment | Gateway, antenna, power and internet | Usually none |
| Number | The mobile number on the SIM | A city or mobile number held by the provider |
| What can fail | A blocked SIM, the box or a power cut | The internet or the provider |
When a GSM gateway makes sense
- Customers have called a mobile number for years, and the mobile operator offers no SIP for it.
- You need a stopgap, for example until IP telephony is connected.
- Calls are few, never more than one at a time.
Before buying a gateway, read your mobile operator’s tariff terms: is using the SIM in a gateway allowed? A SIM used without permission can be blocked, and the number customers know stops working with it.
When SIP is better
- Several calls come in or go out at the same time.
- Staff work in different places, or you use a cloud PBX.
- An AI operator needs to answer your calls.
- You don’t want to look after a box, an antenna and SIM cards in the office.
Example: a courier service
The courier service Chaqqon Kuryer had six SIM cards in a gateway. For example, on a promotion day calls went up, the seventh caller heard a busy tone, and two SIMs were blocked after many outgoing calls. The service moved to a SIP line with a city number and took the channels it needed from the provider. Calls to the old mobile numbers were forwarded to the new one for a while. This is only an example; your numbers will differ, but the logic is the same.
An AI operator and SIP
You don’t need to buy a GSM gateway to connect Sado’s AI operator: it connects over SIP. If your city or mobile number is opened with your provider as IP telephony (for example Sarkor or UTeL), the provider gives a login, password and server address, and Sado’s team sets up the rest. If your mobile operator offers no SIP for the number, a new number can be connected, and we’ll choose the easier route together.
The operator takes more than ten calls at once and makes outgoing calls from the same number. More: AI operator for incoming calls, Sado’s AI outbound calls and about SIP trunks. Try it live or call 78 778 01 23.
Questions
Can I make mass calls through a GSM gateway?
We don’t advise it: many mobile operators restrict this in their tariff terms and may block the SIM cards. Make mass calls only to people who agreed to hear from you, and over a SIP line.
Why does a gateway sound worse?
The sound is converted twice: from the mobile network into the box, and from the box onto the IP line. Where the signal is weak, calls break up. Putting the box by a window or adding an outside antenna helps.
Can I move to SIP without losing my mobile number?
First ask your mobile operator whether it offers a SIP connection for that number. If not, put the new number everywhere and keep the old one for a while.