Release Yealink Firmware V66.85.133.13 for T4-Desk Phone Series

The information in this article applies to the following products:

• Yealink Desktop Phone T41S
• Yealink Desktop Phone T42S
• Yealink Desktop Phone T46S
• Yealink Desktop Phone T48S

Summary 

Enreach has released the new firmware V66.85.133.13 for the Yealink T4-desktop phones series (T41S / T42S / T46S / T48S) for the usage with Swyx 14 and higher.

Information

Firmware required to support the Yealink T4 series from Swyx 14 and higher.

Firmware V66.85.133.13 includes support for the new Yealink Rediretion Services (RPS), which will be put into operation on 1 January 2026. More information on the significance of the Yealink RPS for zero-touch provisioning of Yealink phones to SwyxON can be found here.

Note: The new RPS only comes into play when setting up a new phone on SwyxON, e.g. after a factory reset. Phones already connected to a SwyxON tenant will continue to work.

This firmware version is available on the Swyx Firmware Information Service FIS during the next of this day.

Downloading the firmware and distributing to all connected Yealink phones can be simply done via the Swyx Control Center SCC. All necessary steps are described in the Swyx Online Help.

Manual Download of Yealink T4-Series Firmware

In the context of a standard Swyx installation is no need for a manual download of the firmware and update of certified SIP-phone. Nevertheless there are some use cases where the manual update or the usage of a local download server makes sense or is mandatory.

For that purpose you can find the download links for the firmware here:

• Yealink Desk Phone T4-Series - FW version V66.85.133.13: Download firmware now