Asterisk not answering calls

Hi, I am trying to play around with asterisk, after getting standard analog phone cards. There are two FXO channels on them, one connected to a PBX.

I started off with the asterisk documentation and asterisk does recognize the call being made to it, but I do not get to hear anything on the phone.
Here’s the output:

    -- Starting simple switch on 'Zap/3-1'
    -- Executing Answer("Zap/3-1", "") in new stack
    -- Executing Playback("Zap/3-1", "/var/lib/asterisk/sounds/auth-thankyou") in new stack
    -- Playing '/var/lib/asterisk/sounds/auth-thankyou' (language 'en')
    -- Executing Hangup("Zap/3-1", "") in new stack
  == Spawn extension (incoming, s, 3) exited non-zero on 'Zap/3-1'
    -- Hungup 'Zap/3-1'

Apparently the call is made and recognized but nothing comes out of the phone, I just get a busy signal. Any ideas ?

This might be almost a year late. But I thought someone might need this info. There are two types of telephone cables. One with two internal wirings and one with four.

I have been using the ones with two. Once I’ve exchanged the cable to the 4-wire, things worked just fine.