I'm working on a project where we, amongst other views, have a grid displaying a list of units around the world and their last given status. Each unit can also have a live connection between itself, a central server and a webpage will display this.
Today, we're indicating that a unit has a live connection by displaying a little rss-icon as seen in this image (blue lamp saying "Running Outhole"):
Whenever there's no connection, all we do is remove the rss-icon and slightly change the opacity of the blue lamp (Lamp also changes colors based on a state, regardless of its connection status). The text stays, indicating that whatever value it might have at the moment was the last known status. There's been some debate whether this is a sufficient way of telling the user that the unit is either connected or that the user is looking at historical data.
Ultimately, I guess my questions is whether this form of indicating a live or "not live" connection to the user is sufficient and clear enough?