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 Rare view of 'Panel-switching' Mechanism
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 Return to top of page · Post #: 1 · Written at 9:02:53 AM on 30 April 2019.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 777

Radical 12-ft-high call connection Gizmo!

Used in Manhattan exchanges in 1920's - last one taken out of service in 1983!

Makes different sounds to either StepXStep or Crossbar.


 Return to top of page · Post #: 2 · Written at 10:17:50 PM on 2 May 2019.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 777

Now reading the training manual for this, they say there were already too many exchanges + interconnecting trunks in greater metro NYC - even by 1919 - that the call originator's dialing should no longer control progress of connection in real time. So am curious to see how they electro-mechanically decode & record complete number.

from Manual:
"When direct control is abandoned, there is no longer any object in
having the selectors move by steps, and since the equipment, to work over
such large groups of trunks, is necessarily somewhat large and heavy, it Is
found more practical to move the selectors by means of an electric motor
which will provide ample power and positive motion. In addition to the
abandonment of direct control, it is necessary, in such a large and complicated
installation as that required in a large city, to abandon also numerical
selection, for it is often impractical to make the group of trunks desired
when, say, the digit "9" is dialed, the ninth group of trunks. If it
is necessary to reach the fifth group of trunks when the digit "9" is dialed,
some means must be provided to move the selector over five groups, although
the dialing actually breaks and makes the subscriber line circuit nine times.
It will be seen later that there are also other reasons for doing away with
numerical selection.
Having abandoned direct control and numerical selection, the digits
which the subscriber dials have no direct relation to the groups of trunks to
which the various selectors move in completing his call and the selectors do
not move in unison with his dialing. Therefore, it is necessary to provide
equipment which will receive the dialing from the subscriber, record it, hold
it, change it as necessary, and transmit it to the various selectors so as to
control their movements and direct them to the proper setting. Thls mechanical
operator, or intelligence of the system, is called the "sender."
The principles of panel dial switching are shown diagramatically
in Fig. 7. The terminals over which the selectors move are arranged in flat
vertical rows rather than in arcs, and the selectors are moved by electric
motors rather than by electro-magnets. There is no direct control of selections
by the subscriber dial, but rather, the dialing is registered in, and
the movement of the selectors is controlled by the sender. This allows for
greater flexibility and a more complex and extensive trunking arrangement
than is possible with the use of direct control."

 Return to top of page · Post #: 3 · Written at 12:04:24 PM on 18 May 2019.
NewVista's avatar
 Location: MilwWI, US
 Member since 10 May 2013
 Member #: 1340
 Postcount: 777

By the mid 1920s in London, the world's other mega-city with a challenging number of subscribers, British telephone Authority, eschewing American motor-driven inventions, decided to implement a "Register/Sender" system with stepping devices, calling it the "Director" (said to be "deafening" during peak traffic times!)

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