Phone ports on the router
The Centro Business routers offer various interfaces for integrating telephony devices. The equipment differs depending on the model generation:
| Function | Centro Business 2.0 | Centro Business 3.0 |
|---|---|---|
| Analog (ATA/FXS) | 2 Ports | 2 Ports |
| ISDN (ITA) | 2 Ports | not available |
| DECT base | Integrated (up to 5 handsets) | not available |
| IP phones (LAN) | Up to 10 devices | Up to 10 devices |
Analog telephone on the FXS port (ATA) | (CB2.0 / CB3.0)
- The router has two FXS ports. One analog telephone (without additional bell) can be operated per port.
- The operation of FAX devices is not recommended for data protection reasons.
IP telephones on the Ethernet port (SIP-TA) | (CB2.0 / CB3.0)
- Via the Ethernet connections, up to 10 IP telephones can be connected using the SIP-TA (B2BUA). Further details under SIP-TA.
DECT handsets | (CB2.0)
- Up to five DECT handsets can be registered directly on the integrated base station of the Centro Business 2.0. Further information under DECT.
ISDN telephones on the ISDN port (ITA) | (CB2.0)
No functional guarantee for ISDN
Since the completion of the All IP migration and the phase-out of analog telephony in 2018, Swisscom granted a transition phase until 2021. The Centro Business 2.0 enabled this through an emulated ISDN function. This emulation remains part of the functional scope of the CB2.0, but is no longer guaranteed since 2022.
- The Centro Business 2.0 has two ISDN ports. Two ISDN telephones can be connected directly or up to eight devices via in-house cabling (S-Bus).
- A maximum of two calls can be conducted simultaneously.
- The interface supports only the basic functions (incoming/outgoing calls). Continued use of old ISDN devices is possible but no longer recommended.
Prerequisites for using telephony
- At least one phone number must be registered on the router.
- The telephony LED lights up white or green depending on the subscription.
FAQ on phone ports
What is an additional bell?
An additional bell signals incoming calls acoustically (very loud) or optically (light signals). Older models in particular have high power consumption and can disturb the telephony function of the router.
Which FAX protocols are supported?
The router supports fax transmission via G.711 (In-Band). The T.38 Fax protocol was gradually deactivated at the beginning of 2026.
Why is FAX no longer up to date?
For most applications, more secure digital alternatives exist today. Unattended received documents on paper no longer satisfy modern data protection requirements.
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