Sweep tone tests. Low to high, and high to low. DSCN0469

Sweep tone test numbers were to be found in lots of the larger offices.
In Milwaukee back in the 1970s, they were scattered all over the metro
area in all of the #1 and #5 crossbars and even in the downtown panel
BRoadway exchange. The sweep tests were prefix + 0008. It was an unsupervised line so it could be called long distance and there would be no
bill for the call. (414) XXX-0008. Gone for many years now.

[@AlexisKasperavicius]

Thanks! Nice work!