A fax needs to be answered, however, most of the time the process of answering is automated.
Most fax machines, fax software, and fax services will automatically answer a call after 2 or 3 rings.
Some fax machines (and other variations of fax) have the option for manually answering the call. This option is usually enabled when a fax machine shares a regular phone line and there is a service such as voicemail on the line.
When a fax machine needs to be manually answered, someone needs to be at the receiving fax machine when the line rings and press “start” or “receive fax” (or some variation) to start receiving the fax.
The most common reason is that the fax machine uses the person’s regular phone line.
If they leave the fax machine to automatically answer, either it will answer before their voicemail / answering machine (and they will never receive any messages), or the voicemail/answering machine will answer before the fax (and the fax won’t come through).
The most popular alternatives to manually answering a fax are a separate dedicated fax line, a second phone number with a distinctive ring and a fax machine with DRPD (distinctive ring pattern detection), the use of a TAM module or fax with TAM, and an online fax service.