VoIP Resources VoIP Reviews Desk Phones

Panasonic KX-UT136

by OnSIP

OnSIP reviews the KX-UT136, one of Panasonic's SIP phones, for the hosted and open source market.

Published: July 14, 2011


OnSIP Testing:star_orange_24star_orange_24star_orange_24star_orange_24star_orange_24
Voice Quality:star_orange_24star_orange_24star_orange_24star_orange_24star_gray_24
Ease of Use:star_orange_24star_orange_24star_orange_24star_orange_24star_gray_24

Quick Specs

  • 4 SIP Accounts
  • 4 Soft Keys, 12 feature Buttons
  • 24 Programmable Buttons
  • HD Voice & Power Over Ethernet (PoE) Support


  • Changes made in web admin portal pushed to phone immediately
  • Large 242 x 109 backlit LCD screen


  • White noise on speakerphone - now less of an issue
  • Has issues receiving REFERs - resolved with new firmware update

Note: The KX-UT136 has since been discontinued. 

Multinational consumer electronics giant Panasonic recently announced the introduction of a new line of SIP phones for sale in the US. It's always nice to see another big player further embracing SIP.

The company's new KX-UT1XX series comprises models that are far more “traditional” desk phone than the company's earlier cordless SIP devices, which makes them better suited for most office environments.

We managed to get our hands on the Panasonic KX-UT136 for testing and review. This top of the line model features a 242 x 109 pixel backlit monochrome LCD, 24 programmable feature/functionality keys, and supports up to 4 SIP registrations.

Phone Configuration

We've added a new way to configure your Panasonic phones if you are an OnSIP customer. If you are not an OnSIP customer, please check this section in the review of firmware version 00.032.

OnSIP Testing

When we last reviewed firmware version 00.032, we cited problems with the way this phone handled REFERs:

We found that the Panasonic KX-UT136 does not behave properly when it comes to receiving REFERs, which means that you will have difficulty trying to transfer callers who are using this phone.

This is problematic for a number of reasons. If you are an OnSIP customer, you probably have a public-facing company number that is linked to an auto-attendant. When callers reach the auto-attendant, they are given the option to dial numbers for departments or dial your employees’ extensions.

Our auto attendant works by transferring incoming callers to the appropriate destination. Chances are that you won’t get anywhere if you’re calling in using the Panasonic KX-UT136. That’s a big problem.

The phone can send REFERs fine, which is why blind and attended transfers work without a hitch when it is the initiator. Try to transfer this phone during a call, however, and you’re likely to run into issues.

This isn’t really a violation of a SIP RFC, per se; it just doesn’t follow the SIP RFC that we use. We’ve spoken in detail about the issue with Panasonic, and it seems like they will address this in the next firmware update, which should drop sometime in the fall.

This issue has since been fixed. The Panasonic KX-UT136 now passes our interoperability tests with no outstanding issues.

Voice Quality

Speakerphone quality has also been noticeably improved. When we reviewed this phone with firmware version 00.032, we found a distracting amount of white noise whenever we switched a call to speakerphone. We're no longer experiencing this problem with firmware version 01.133.

Learn more about VoIP Reviews