[channels]
        context = default
        switchtype = national
        usecallerid = yes
        echocancel = yes
        echocancelwhenbridged = yes
        ;add the is option if you are problems with DTMF detection
        relaxdtmf = yes
        rxgain = 0.0
        txgain = 0.0
        signalling = fxo_ks
        group = 1
        channel => 1-4

[channels] 
         context = from-pstn
         switchtype = national
         usecallerid = yes        
         echocancel = yes
         echocancelwhenbridged = yes
         ;add the is option if you are problems with DTMF detection
         relaxdtmf = yes    
         rxgain = 0.0
         txgain = 0.0
         signalling = pri_cpe
         group = 1
         channel => 25-34