Several Honeywell systems are available to upgrade their cellular communications, This is a breakdown of what is able to upgrade and what must be done to allow this update. 

The Honeywell Vista 21ip must be at least a Revision 3.18 in order for it to be upgraded to 4G, there is often an indicator sticker on the actual board where the communicator would be installed that states if it is upgradable or not. If it is not capable then external communications is also possible using a GSMX4G, CDMA-X4G, GSMV4G or an IGSMV4G. There is a jumper switch on the main board that will also need to be repositioned in order for external applications to be utilized.

The Honeywell Vista 10p can only be upgraded to 4G when used with a universal communicator referred to as the TG-1 Express

The Lynx Touch Series (with exception to the Lynx Touch 5000) can all be upgraded to 4G without the need of a chip swap or firmware update

Currently, the Vista 15p/20p / Safewatch Pro 3000 are the only panels that can be changed with a chip swap. Chip swaps may be necessary in order for the panel to be compatible with the 4G communications. These panels are the most popular used when it comes to regular use and upgrading its communications.