Heartbeat network vs intranet - their both working method is working within computers in a specific system? Both of them don't make a request via internet (to outside of a building via air or cabel)?
Wikipedia says:
...Heartbeat network is not accessible from outside the cluster.
...Intranet is accessible only to an organization's staff.
Am I right if I say that their connection to outside of a building is disabled?
No. Their status of being within a particular area does not preclude the ability of machines within those areas being connected to the Internet. Those machines themselves will probably not be accessible from the internet or wider network, but there is no reason to assume that they cannot access the wider network themselves.
To put it in perspective, your home router has a webpage. If that webpage is only accessible by your home network devices then that technically is an "intranet" website, your home network is technically an intranet. The computers within your home network can still access the internet but, unless you have configured port forwarding or set up the router to allow remote administration then people on the wider internet cannot communicate with your machine without you initiating the connection first.
This is mainly a question of prefixes. Specifically the inter- and intra- prefixes. "inter" means "between" so "internet" is "between networks". "intra" is "within" or "inside" and so "intranet" means "within a network"
Just because you are within a particular network does not mean you cannot access other networks.
The "heartbeat network" appears to be a specific use case for an intranet. It is a small cluster of computer nodes monitoring each other over a small network in order to maintain reliability. The machines presumably still have connectivity to the internet, but their "I am still alive" (heartbeat) information is kept within their small "private" network.
