Answer the call for a channel.This sets up duplex audio between the calling ''A'' leg and the FreeSwitch server. It is not about other endpoints.
The server might need to 'answer' a call to play an audio file or to receive DTMF from the call.
Once answered, calls can still be bridged to other extensions. Because a bridge after an answer is actually a transfer, the ringback tones sent to the caller will be defined by
Play A Tone
A simple example to answer in order to play a 1004kc test tone to the caller, then hangup.
Answer a Call to Detect FAX Tones
We need to answer the call to let FreeSWITCH receive the audio to start detecting FAX tones. Because a bridge after an answer is actually a transfer, the ringback sent to the caller is now defined by transfer_ringback