Central Office Equipment
In almost every neighborhood there is a windowless building that houses the
switching equipment that connects your telephone to your neighbor's telephone
or routes your call to another central office for long distance calls. This
building is called the central office. The switching equipment is located on
panels in the central office. The museum has six operational panels of
different vintages on display.
Master Test Frame for #5 Crossbar Switch
This frame uses relays to test other frame circuits. Today the equipment is
computerized and is uses digital components. Our modern computers are direct
decendants of the switches developed for telephone circuits.
#5 Crossbar Frames
This view of the #5 crossbar shows several frames one behind the other. The
frame that is closest in the photograph is the automatic monitor test frame.
The frame just behind it is the master timer that tallies the toll charges for
subscribers. The next frame after that is the automatic test frame.
Panel Final Frame
This is a close up of a panel final frame it shows a terminal bank and select
rods and the rotary sequence switches unique to the panel office. The rods are
driven by electric motors and clutches and move up and down to make
connections. On the left of this photograph, sequence switches control the
operation of the rods. This office has been returned to operational condition
and is thought to be the only operational unit remaining in the world.
Community Dial Office
This community dial office utilizes Strowger designed switches. These switches
were manufactured by Western Electric. These rotary switches had contacts that
were 10 switches high each with 10 positions. Pulses created from the
suscriber' s rotary dialer cause the switches to rotate and connect to the next
series of switches for each digit that was dialed. The Strowger equipment shown
was originally installed in Crystal Mountain, Sumner and Belfair, Washington.
Pieces of equipment were assembled to create this working display.
Main Distribution Frame
The main distribution frame (MDF) is located in the central office (CO). This
frame terminates (connects) all the wires and cables that enter or exit the
central office. The MDF contains fusible links to protect equipment from damage
from lighting or other voltage surges.
Home Page
This view of the #5 crossbar shows several frames one behind the other. The
frame that is closest in the photograph is the automatic monitor test frame.
The frame just behind it is the master timer that tallies the toll charges for
subscribers. The next frame after that is the automatic test frame.
This is a close up of a panel final frame it shows a terminal bank and select
rods and the rotary sequence switches unique to the panel office. The rods are
driven by electric motors and clutches and move up and down to make
connections. On the left of this photograph, sequence switches control the
operation of the rods. This office has been returned to operational condition
and is thought to be the only operational unit remaining in the world.
This community dial office utilizes Strowger designed switches. These switches
were manufactured by Western Electric. These rotary switches had contacts that
were 10 switches high each with 10 positions. Pulses created from the
suscriber' s rotary dialer cause the switches to rotate and connect to the next
series of switches for each digit that was dialed. The Strowger equipment shown
was originally installed in Crystal Mountain, Sumner and Belfair, Washington.
Pieces of equipment were assembled to create this working display.
The main distribution frame (MDF) is located in the central office (CO). This
frame terminates (connects) all the wires and cables that enter or exit the
central office. The MDF contains fusible links to protect equipment from damage
from lighting or other voltage surges.