How to configure a Linksys PAP2T ATA to connect an analog fax machine to Asterisk

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I was having problems getting a Linksys PAP2T-NA to work with Pitney Bowes mailing station so it could use its modem to dial home and download postage/software updates. After scowering the web, I couldn’t seem to find a definite how to article on what settings were needed. I finally came up some settings by combining the information from various places around the ‘net. I have typed out those settings and included them below.

I was using a Linksys PAP2T-NA with firmware version 3.1.15(LS), but I would assume that these settings would be similar on the Sipura SPA-1001, and the Linksys PAP2, SPA2102, SPA3102.

Settings that have an asterisk (*) before them seem to be particularly important, so please make to pay attention to them.

SIP (tab):

RTP Paremeters” section:

*RTP Packet Size: 0.020 (or 0.010)


Line (tab):

Network Settings” section:

*Network Jitter Buffer: very high (or extremely high)
Jitter Buffer Adjustment: disable


Supplementary Service Subscription” section:

*Call Waiting Serv: no
Block ANC Serv: no
Cfwd All Serv: no
Cfwd No Ans Serv: no
Cfwd Last Serv: no
Accept Last Serv: no

Call Return Serv: no
*Three Way Call Serv: no

Speed Dial Serv: no

Service Announcement Serv: no
Block CID Serv: no

Cfwd Busy Serv: no
Cfwd Sel Serv: no
Block Last Serv: no
DND Serv: no

Call Back Serv: no

Secure Call Serv: no


Audio Configuration” section:

Preferred Codec: G711a (or G711u)
Use Pref Codec Only: yes

FAX Codec Symmetric: yes

Hook Flash Tx Method: None

*Silence Supp: No
Silence Threshold: medium
*Echo Canc Enable: No
Echo Canc Adapt Enable: no
Echo Supp Enable: no
FAX CED Detect Enable: yes
FAX CNG Detect Enable: yes
FAX Passthru Codec: G711a
FAX Passthru Method: NSE
FAX Process NES: yes
FAX Disable ECAN: yes