How do I install a 7847i Internet Communicator to the Vista 21iP Control Panel?

You should not have to install the 7847i on your Vista 21iP because it already comes with a 7847i internet communicator built directly into the board.

However...

In the rare case where the built-in communicator is not functioning properly, you would need to install a 7847i to your Vista 21iP the same way you would with just about any of the Honeywell Vista Panels.

Open its enclosure by pushing in the tabs located at the bottom of the 7847i. Use screws and wall anchors to wall-mount the unit. Insert an Ethernet cable into the device and connect the other end to your router. Then connect the 7847i to your Vista 21iP control panel using a four-conductor wire.

Turn off the control panel completely by disconnecting the AC transformer and one back-up battery lead.

Connect the communicator's 3rd terminal to the control panel's 5th terminal with a wire. Then connect the communicator's 4th terminal to the control panel's 4th terminal using a second wire. With a third wire, connect the communicator's 5th terminal to the control panel's 7th terminal. Lastly, connect the communicator's 6th terminal to the control panel's 6th terminal.

Shut the 7847i enclosure, turn on the Vista 21iP, and the communicator should be up and running.

A 7847i Communicator is important because...

it gives your system a back-up line of communication in case your copper telephone line becomes damaged or cut.