What happens if the line is busy or there is no answer when receiving a TTS call?

tyntec’s 2FA API detects the number type (landline or mobile) and by default decides the delivery channel to send the OTP. For fixed (landline) numbers, tyntec will use a TTS call, while SMS is the primary delivery channel for mobile numbers.

This is set by parameter via with the following possible values:

  • AUTO (will use SMS in case of mobile number and VOICE in case of landline)
  • SMS

Because the 2FA API is a highly customizable product, you can overwrite this algorithm and choose the delivery channel independent of the number type. This, however, might impact the probability of successful verification.