Joe, it is used for the splicing of outside plant cables. As Bill said, instead of splicing one pair at a time, this system allows a splicer to lace 25 pairs into a module and crimp/cut/splice them with one throw of a handle. A HUGE labor-saving system that was developed in the 70's.

3M has pretty much bought this system. It was first developed by Western Electric. After the multiple transitions of AT&T, Avaya abandoned this segment of the industry and other manufacturers took over. PSI was the most predominant, a WECO sub that made their 2- type ("Waffle") splice closures.

Most major telcos use either the original 710 system or 3M's original MS2. Splicing by the pair is pretty much a thing of the past except for maintenance of old plant.

Ed Vaughn, MBSWWYPBX