What is a Joint Staff approved, standardized communications link that is suitable for the transmission of digital information and is characterized by a standardized message formats and transmission characteristics?

TDL (Tactical Data Link).

Explanation:

TDL is the authorized, formalized communication connection for electronic information transfer and it is identified by formalized communication types and transmitting features.

It is used by the join staff for the standardized connection or also for the communication.

So, the following answer is correct according to the scenario.