The snom m3 SIP wireless (DECT) phone is one of my favorite VoIP phones. I've been testing and reviewing it for a few months but haven't had time to write up the review until now. First, let me point out that the problem with IP-PBXs is they typically give you a desk phone or a softphone with no real mobility options to walk around, which is critical in some vertical markets, such as retail and manufacturing. Even sales professionals want the flexibility to take calls while roaming the office. In the past, I have used analog telephony adapters to connect my cordless phone to my SIP-based IP-PBX, but the cordless phone lacks multiple lines, call transfer, call conference, call waiting, or even a message waiting indication (MWI). Enter the snom m3, a SIP wireless phone that like a home cordless phone which not only gives you mobility while on the phone, but full IP-PBX functionality as well, including call hold, call transfer, message waiting indicator, and more. In fact, while the caller is holding, music-on-hold is available from the IP-PBX, giving the same business professional experience from a desktop phone.
I should mention that there are WiFi SIP phones, but the battery life on these phones isn't great. snom takes advantage of Digital Enhanced Cordless Telecommunications (DECT), a wireless communication standard which can seamlessly hand off calls as a handset moves between multiple base stations in a large office, but also has superior battery life than WiFi SIP phones. The Lithium Ion battery offers a very good eight hours of talk time and 100 hours of standby. Additionally, DECT devices use the 1.9 GHz band while WiFi uses 2.4Ghz so they don't interfere with one another. DECT also doesn't suffer the microwave oven interference that often plagues WiFi access points.
snom m3 Main Menu
The snom m3 supports up to 8 different SIP identities (registrations) allowing you to connect to separate IP-PBXs (or SIP service providers) or the same IP-PBX to support multiple lines. The m3 is 2" x 5" and less than an inch thick sporting a nice 1.75" color LCD (128x128 pixels and 65,536 colors), 2.5mm headset jack, and a speakerphone. The headset jack is a nice feature that I haven't seen on any cordless DECT phones. The phone also comes with a belt clip so you can easily use the headset for talking while walking. The m3 is surprisingly very lightweight - much lighter than I would have expected. The phone also has volume controls, the basic 12 dialpad keys, five navigation keys, and two function keys. The snom m3 ships with some documentation, but for real technical details, the snom m3 wiki is the place to go.
The m3 communicates with the base station which is connected directly to your network via a standard Ethernet cable. Once connected and booted up, the base station obtains an IP address from the DHCP server. By default (factory setting), snom m3 phones are configured to use HTTP as the transfer protocol for provisioning, but TFTP can also be used. Since I was testing this with an Asterisk-based trixbox system, I changed the gateway to use TFTP. Also, the snom m3 supports Option 66 on the DHCP server to automatically acquire the IP address of the TFTP server. Nice!
The TFTP boot server address can be an IP address, a fully qualified domain name (FQDN), or an URL. I also created a config file (/tftpboot/m3/settings/0004132A10E4.cfg) on the TFTP server for the snom m3 to download. I was able to get access to the firmware, upload the new firmware to /tftpboot/m3/firmware/ and it automatically downloaded the latest firmware. Even better you can have it set to connect directly with snom's server (http://provisioning.snom.com/m3/firmware/) to download the latest firmware (1.20) and even set a schedule to automatically grab the latest version.
- Display: 128 x 128 pixels, 65536 colors, backlit
- Li-Ion battery pack for 20 hours of calls or 100 hours standby
- Range: 50 meters indoors, 100 meters outdoors
- 12 numerical keys, 5 navigation keys, 2 function keys
- Speakerphone on mobile handset
- Polyphonic ringtones
- Automatic registration of handset
- Separate charging cradle for handset
- 8 handsets per base station
- 8 SIP registrations with different servers/registrars
- Up to 3 concurrent calls per base station
- Three-way conference
- Remote setup, password protection
- Open DECT GAP standard
The snom m3 supports the most common VoIP codecs, including G.711u (PCMU), G.711a (PCMA), G.729ab, and iLBC. G.711 is the standard used by traditional phone systems and it features the best voice quality at the expense of more bandwidth used (80kbs), which isn't ideal for some DSL connections that only sport 256kbs upstream. Fortunately, the snom m3 supports G.729a which only use 8kbps at a slight loss of voice quality. iLBC (Internet Low Bitrate Codec), although not as widely supported, is designed for narrow band speech and supports two bit rates, 15Kbps (20ms frame rate) and 13.3 Kbps(30ms frame rate), though the m3 only supports the 20ms frame rate @15Kbps. iLBC yields slightly better voice quality than G.729a yet also has a higher robustness in dealing with packet loss while using roughly the same amount of bandwidth. It also has a more dynamic range of sound than G.729a. So kudos to snom for including iLBC as a choice.
You can also configure various settings from the phone itself, though it's more tedious. The VoIP settings is protected by a PIN / password which defaults to 0000. From the phone you can configure the timezone and it even supports NTP time servers for accurate time. Additionally, you can add contacts, however adding contacts via the phone is a bit tedious. I wished the web interface let me add them there and then it would push the contacts down to the multiple handsets.
Update: 10/8/08 - snom's latest m3 firmware 1.20 now lets you upload a .csv file to the gateway (common/shared contacts) or to an individual handset after going into the Directory settings. Here's a screenshot of the Directory feature that now displays after I upgraded the firmware on my m3:
So how's the phone's range? snom claims the phone needs to be within 50 meters indoors or 100 meters outdoors from the base station. I walked around TMC's offices and didn't lose a signal. Then I went outside walked about 250 feet and it was crystal clear. Excellent range I have to say. The voice quality of the earpiece was very good and the remote end said I sounded very good during my test calls. I also tested the speakerphone, and although it wasn't the best voice quality, I didn't expect a fantastic sounding speakerphone on such a small handset. I should mention that you can also perform intercom calls to either a single m3 handset or you can intercom page all handsets. Useful if you are trying to reach someone and don't know where they are located.
You can buy the snom complete set (with base + handset) on Amazon for ~$170, and an additional handset on Amazon for $134.