OUR MISSION
is to demonstrate the social and technical significance of the telephone network
from 1876 to the present, using working equipment to provide tangible,
operable evidence of an evolving technology.
WE CELEBRATE
the inventiveness, craftsmanship, ingenuity and industry
of the telecommunications community through educational programs,
exhibits, and special events.
"It's for YOU"
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| Number 5 Crossbar System |
Yes, after many years of work, the number 5 crossbar can finally make telephone calls. Getting the switch to this this stage has meant a tremendous amount of work from a number of Museum volunteers. The switch arrived at the Museum in pieces and it was necessary to assemble the various bays and then figure out how to wire them all together to make a working unit. Old wiring had to be stripped off, countless feet of cable had to be been run, and well over 5,000 wire wrap terminations were made. (There were a number of wrong connections made as well, although as luck would have it, it did not take too long to locate and fix them.) Much time was also spent studying the documentation – number 5 crossbar is a complicated system, and it was essential to fully understand how all the pieces fit together before attempting any of the wiring. Fortunately, the Museum owns a rich set of documentation for the number 5 switch, including some excellent training materials that were intended for telephone company personnel who worked on number 5. The training materials in particular were of great help in understanding how the switch worked and how to put it back together.
Our number 5 crossbar switch originally served as the central office for Belfast, Maine, and handled about 6,000 subscribers. The Museum does not own the entire switch, only sufficient representative parts to demonstrate its workings. Nevertheless, it is currently the Museum's largest exhibit, occupying about a half of the bottom floor of the barn. Not having all of the switch meant that some “re-engineering” had to be done – working out how to connect together those parts of the switch that the Museum does own in the absence of the other parts.
There's still a lot of work to be done just to get the switch in the state where museum visitors can make calls for themselves. Firstly, some more telephones need to be connected. (Right now there are only two temporary telephones connected.) Secondly, some of the switch's error-checking circuitry is not yet operative, so if a wrong number is dialed, the switch will lock up, leaving the caller with dead air and not allowing further calls to be made. This will be fixed this fall or next spring. We hope to have a “grand opening” of the exhibit next summer. Beyond that, additional work on the switch will allow it to connect calls to the various other switches at the Museum.
The work described here could not have been done without the assistance of many Museum volunteers; thanks to Jeff Birkner, Charlie Dunne, Chad Perkins, Dave Thompson, Rick Walsh and Rick Miller for their invaluable assistance throughout the project.