This phone was given to Miss Richmond by Clarkson. It may be what's referred to when Miss Richmond asks Vanessa if she packed "it". If so, then it can't be interferred with by the academy. It was later seen being carried by Vanessa Richmond.
It is a military prototype of a long distance two-way radio communicator that only work at the academy. It was made by Clarkson; it can only be seen and used by Ellen and Vanessa; if she tells anyone about it they will immediately forget about it. The radio seems indestructable: after breaking it at the camp, Ellen was able to receive a message from the older Vannessa that is locked in the cells of the academy.