The ideal system involves strapping all the incoming and outgoing lines to the PABX together. With this system, there is no potential difference between the incoming or outgoing lines, thus the equipment is protected. The only problem is that the equipment will not function.

Should we try and simulate this system, we find the additional problem of long lead lengths connecting devices to ground. With fast rising transients (lightening), large volt drops occur along these leads due to induction, which renders all protection ineffective. Even though the protection units would function individually, the installation method would create differences in potential between the various points and thus damage on the equipment will occur.