Zenith System 3.

[zeno]

Originally Posted by Rod Beauvex

Wait, what? So the sets still worked with the spark bulbs fried?

Here is the gap I was talking about.

http://www.google.com/patents/US4438365

There were a few slightly different styles. The 3rd wire went to the TV's
cold ground. Find it in any Zenith from late 1970's through the
one board paper mache PCB's of the 90's.
Most sets are on cable. This puts the TV cold ground to earth. Power
line gets hit & it arcs across to earth instead of using the high
resistance path through all the delicate stuff like IC's, tuners,
thin etches etc. Or it can just arc across the line.
Some makers printed them on the PCB but they were not as
close spaced so not to effective.
If I were building a project or protecting something of value I
would use one, just be sure to use it AFTER the line fuse.

73 Zeno