Tuning the phones

Written early in the evening in English • Tags:

I spent some time with my parents about a month ago fine tuning the echo cancellation on our SIP phones. Today I got a chance to refresh my memory while connecting the phones of a friend to a CallWeaver PBX I had setup for him. Hopefully I have now collected in one place all the settings that were changed from the factory defaults. If you have a Linksys SPA3102 phone adapter or a Linksys SPA942 phone, you may find some useful hints in here.

First navigate to the advanced voice administration pages on your device:

  • Linksys SPA3102 / SPA2102: Admin Login > Advanced > Voice
  • Linksys SPA942: Admin Login > Advanced

The following settings work well for me:

Tab Section Setting Value Remarks
SIP RTP Parameters RTP Packet Size 0.020
Regional Miscellaneous Time Zone GMT +02:00 Finland
Daylight Saving Time Rule start=3/-1/7/3;end=10/-1/7/4;save=1
(European Union)
Ring and Call Waiting Tone Spec Ring Waveform Sinusoid Finland
Control Timer Values Hook Flash Timer Min .05
Miscellaneous More Echo Suppression yes
(Siemens Gigaset 3000)
FXS Port Input Gain 16
FXS Port Output Gain -15
Caller ID Method Bellcore (N.Amer, China)
Caller ID FSK Standard bell 202
(Siemens Gigaset E450)
FXS Port Input Gain 0
FXS Port Output Gain -3
Caller ID Method DTMF (Finland, Sweden)
Audio Input Gain (dB) Handset Input Gain 6
Headset Input Gain 0 Hello Direct Unaural
Acoustic Echo Canceller Enable yes
Ext 1-4
Line 1-2
Network Settings Network Jitter Level low Echo suppression
Jitter Buffer Adjustment up and down Echo suppression
Proxy and Registration Register Expires 120 Notice network problems faster
Supplementary Services Date Format day/month
Audio Volume Back Light Timer 30 s Maximum timeout


  • 1


    I’ve been looking at buying some Linksys SPA942 phones. Would you recommend them?


    Bert Balliss — 11.1.08 @ 19:06

  • 2

    Hi Bert,

    The SPA942 does everything I need from a phone. I like the multiple line keys so it is easy to see from afar which line is ringing. The backlight is essential for clear reading of the display (and this is why I chose SPA942 over the SPA941). The built-in headset jack is also one of my favorite features, and it has a dedicated key on the phone set. Message waiting indication (MWI) works perfectly and includes per-line indication.

    I have not setup call transfers or conference calls through Asterisk yet, as these features have worked fine for me as implemented on the SPA942. Eventually I want to use Asterisk for those, though.

    The PA100 power supply (not included with the phone) is unfortunately wide, even if it is not the biggest power supply I’ve come across. I’ve just ordered more SPA942 phones, but I’ve bought other power supplies this time in a narrow form factor, better suited for those crowded power strips. Of course, if you have power-over-ethernet (802.3af) support on your network, you won’t have to worry.

    From what I’ve read, shared (or bridged) line/call/extension appeareances are not implemented in a way compatible with Asterisk. Since I have a PBX background, I’m much happier with call parking anyway. However, if you are used to working with a key system, this might be an issue for you.

    Kimmo Suominen — 12.1.08 @ 21:18

  • 3

    Thanks for the detailed reply.

    The PA100 power supply (not included with the phone) is unfortunately wide

    Ah that’s worth knowing. It’s a pet hate of mine when power supplies overlap the neighbouring sockets too.

    Bert Balliss — 14.1.08 @ 12:30

  • 4

    I thought I had good enough quality power supplies picked for the phones, but unfortunately that was not the case. The alternative power supply was causing a buzzing sound, which also threw echo cancellation out of whack. Back to the PA100…

    Kimmo Suominen — 22.1.08 @ 15:33

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