A Hero vFax number replaces a physical fax machine by using email to send and receive faxes using our fax gateway as a go-between your office and the sending or receiving fax machine.
T.38 Fax protocol explained
Our fax service uses the T.38 protocol to transmit faxes via the public internet. While not quite as reliable as your old PSTN fax service, if you are happy to ditch your old fax machine you’ll find our service successfully communicates 95 of 100 fax transmissions. However, before deciding to go with our fax-mail service you should consider the following scenarios which are known to hinder transmission reliability.
- Receipt and Delivery: Ideally we recommend substituting your fax machine with your email client to both send and receive faxes.
- High Speed fax: One of the ways t.38 attempts to reduce the jitter or packet loss normally fatal to IP faxing is to reduce the communications speeds down to a 14.4kbps rate. The problem arises with some lower cost fax machines unable to negotiate from 56.6kbps to down to 14.4kbps causing a transmission failure.
- Colour fax: At CloudPBX IP faxing is black and white only. While most colour machines will negotiate down to our black and white, some machines can’t negotiate to B&W which will cause transmission failures.
- Auto Answer fax machines: We cannot communicate with fax answer machines in answer machine mode. The recipient will need to disable the answer machine to receive the incoming CloudPBX transmission.