Before you can use a Y cable between your Leica TPS total station and a FieldHawk radio you have to confirm the following:

Typically the Leica Y Cable that has two Lemo ends and a battery connector (part #409684) needs to also include a GK1 Lemo to 9 pin DB9 adapter (part #707525).  The adapter is what allows you to connect the FieldHawk base radio to the Y cable.

These parts can be purchased through your Leica dealer.