Phantom Power Attenuator & DC Blocking Capacitors?

I have a body pack for a lapel mic made by sure that we were wanting to use for wireless computer, ipod, ipad audio on A/V carts at our college. We found a Shure TAF4 to XLR cable were were going to order and convert from XLR to 1/8" TRS. It was mentioned to us that we would need an Atteunator and DC Blocking Capacitors to prevent damage to the user end equipment. Can someone explain why we would need this? I kind of understand the term Phantom Power but dont understand why it would damage the user end equipment?