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Northern Electric N501F Box??

Started by axil, June 04, 2016, 09:36:00 PM

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axil

Hello I found this box in a lot of old parts. It has N501F stamped on the back. I'm curious as to what this was used for?
My first guess was some sort of fuse box but i,m not sure??
thx

unbeldi

#1
Fuse box!   wow.

No, this is a subscriber set for a way station telephone along a railroad track.

Since railroads are long and a single pair of wires has to connect potentially dozens of stations, these subscriber sets are designed for extreme efficiency.   They cannot be operated with a conventional telephone system, because of the high impedance provided by the No. 42 induction coil.  You might notice how big it is.  It weighs almost exactly one pound by itself.

In these railroad stations, the induction coil is in series with a condenser (in the metal can) bridged across the line, permanently, as the station has no hookswitch to disconnect it from the line. This affords a condition so that the characteristics of the line do not materially change whether one or all of the stations are listening at the same time, which is likely for announcements from a dispatcher.

Typically, this subscriber set was paired with either a scissor-type transmitter arm, such as the No. 48D (1048, 1148, 1248, or 1348 telephone), as pictured below, or with a desk stand, all having a headset instead of a hand-held receiver.  Since this is Northern Electric variety, they may have also had some other sets to pair with, perhaps even a railroad Uniphone?  All that is needed is a transmitter and receiver, and the hookswitch.  Typically, though, they would use a high-efficiency transmitter and receiver, such as F2 and HA2.

The subscriber set requires a push button to switch the unit into talk mode,   push-to-talk.  In the 501E, this pushbutton was mounted in the wood side of the set, but your 501F was designed for an external foot-operated switch.

The 501E/F sets were the successors to the 501A/B, which had been made since the early 1920s.  I think the only differences are new materials available in the late 1940s.  The circuits were otherwise identical.

axil

awesome! thx for the great explanation.

unbeldi

Quote from: axil on June 04, 2016, 10:30:15 PM
awesome! thx for the great explanation.

How do you just find something like this in a box of parts?  LOL.

You can make it work if you have two of them, because two would have matching impedances and could talk with one another.

axil

LOL Actually its from an auction with a mixed bag of old phone parts from the same era and this was one of them. The other stuff i've seen before like ringer boxes etc etc but unfortunately there's only one of these.