I am in the process of installing a dichroic head in a 23CII, but i can't figure out how to disconnect the power supply from the cold head that it came with!

The connection looks like the following images.



I have no idea what to do with this connection. Both ends unscrew, but they just seem like caps to protect the stripping. The middle bridge has a 'press' instruction, but no matter how hard i try (not too hard!), it's incompressible.

Can anyone give me a hint?