This is somewhat of an obscure feature in that it doesn't come up in most applications. But in some circumstances, it can be really useful:
An ACENet device can be shared between multiple Telestra Targets.
What this means is that you can have two Telestra targets running layouts, and an operator on one physical channel of a given ACENet device (say, an ACE-RIU) is "connected" to one Telestra, and another operator on a different physical channel of the same ACE-RIU is connected to the other Telestra.
In effect, each Telestra is using "half" of the ACE-RIU as a separate, independent ACENet device.
When would that be a useful thing to do? Here's one example. I have a customer with an application that has two Instructors on an ACE-RIU. The application has separate Telestra Targets for the IOS and the Aircraft crew simulation. In one training scenario (of several), one of the Instructors becomes a Pilot Role Player, ie. he is acting as one of the crew. In order keep the simulation realistic in terms of shared sidetone, correct crypto tones, etc., the Pilot Role Player position needs to transmit and receive on the crew radios, which are simulated on the Aircraft/Crew Telestra.
By sharing the ACE-RIU between the two Telestras, we can create a layout that, when needed, has the PRP position connected to the Crew Telestra, and the Instructor next to him connected to the IOS Telestra, and they are both on the same ACE-RIU. When you change layouts to support another scenario, both operators on that ACE-RIU are connected to the IOS Telestra.
It's subject to some restrictions, though:
Also note that this is a Telestra feature only, it's not supported in Voisus.