You register with this service, get a new phone number from them that they auto-answer, then provide this number to the security service. When the security service calls this number, it will play back DTMF codes to simulate whatever buttons you need to press to enter your code key.
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You register with this service, get a new phone number from them that they auto-answer, then provide this number to the security service. When the security service calls this number, it will play back DTMF codes to simulate whatever buttons you need to press to enter your code key.