help with nst

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "colin.heath4 by way of Terry Fritz <twftesla-at-qwest-dot-net>" <colin.heath4-at-ntlworld-dot-com>

hi all,
        my fart nst has a terminal on it marked with a square shaped e ne1 know
what it is? its next to the earth terminal
 
also it appears to be a weaker output than it used to be. can these units break
down slowly?
 
its 6kv 25ma but does not draw the same arc it used to on output wires and the
sound of my tc is not the same, also the sparks from toroid are also thinner
than they were
this happened after i opened the gap too wide