Using mobile hotspot as internet backup

Hi, I have a client who needs an always-on internet solution at their business. They currently have a normal broadband connection, which is spotty at best. I would like to add an AT&T LTE USB adapter, and use it only if the broadband goes down.

Does the Peplink Balance 20 offer the feature I am looking for?
Does it support a LTE USB adapter such as
Does it offer seamless integration between the two connections (ie…without having the users ever noticing)?

Thank you!

Yes, the Balance routers all have this feature anf the Beam is indeed a supported modem. When the broadband goes down all traffic will automatically switch over to the USB modem. Thanks.