Interesting Bell System Map

[Sargeguy]

This picture was sent to me by the mother of one of my daughter's classmates.  It belonged to a relative:



She considers it a family heirloom and would like any information about her ancestor that can be gleaned from the map. 

[NorthernElectric]

Seems to be lots of information on the web re. Harry B. Coxhead.

A few tidbits I found related to the map were patents in the US and Canada related to his work on ship to shore and/or radio telephony.

Also marked on the map is Madison, WI where he apparently attended University.  Here's his 1914 yearbook.

Is this the sort of info you were looking for?

[Sargeguy]

Thanks,
Here is what I already sent her:

• The map is hand drawn and tracks the owner's career through the Bell System.  It looks like he worked for Bell Labs, the research division of the Bell System.
• Harry B. Coxhead invented a signalling system for mobile phones back in the 50s, an important milestone in the development of cell phones.
• The figure in the upper right hand corner is a rendition of the "Spirit of Communication", a statue commissioned by AT&T and used occasionally as the Bell System/Bell Labs/Western Electric logo.
• The line "May you always find that extra jack" refers to telephone jacks. 
• From the Bell Laboratories Record, July 1946:  HARRY B. COXHEAD visited the White House to consult with the staff regarding communication matters. 

[Sargeguy]

Also like to golf:

[Sargeguy]

This explains why the picture of the radio she sent me has a handset:

[AE_Collector]

• The line "May you always find that extra jack" refers to telephone jacks. 

Not certain about that. Telephone Jacks as we know them didn't exist when he retired in 1957 (18 days after I was born) and i doubt that even the 4 prong jacks existed yet.

But switchboard jacks existed and since he seems to have spent his career working on what would be used for trunking it might be that he was always looking for spare jacks on toll boards to connect his trial circuits to for testing.

Terry

[DavePEI]

This explains why the picture of the radio she sent me has a handset:

Not so much. This is a crystal radio, and crystal radios required high impedance receivers - a telephone handset would not have worked with them. The low impedance of the handset would have loaded down the radio so much, it wouldn't have operated.

Note the crystal detector and cat's whisker on the upper right board, the tapped coil, and switch to change taps.

The only thinh I can see is she might have layed the handset on top of the radio because she thought it belonged to it.

Dave

[poplar1]

• The line "May you always find that extra jack" refers to telephone jacks. 

Not certain about that. Telephone Jacks as we know them didn't exist when he retired in 1957 (18 days after I was born) and i doubt that even the 4 prong jacks existed yet.

But switchboard jacks existed and since he seems to have spent his career working on what would be used for trunking it might be that he was always looking for spare jacks on toll boards to connect his trial circuits to for testing.

Terry

283-type 4-prong plugs and 404-type jacks were introduced for portable anti-sidetone telephones around 1931-1932. And, before that, there were 3-conductor plugs and 273-type jacks for portable sidetone telephones.

[Sargeguy]

The owner was experimenting with radio telephony, so this thing doesn't necessarily need to have been successful.  The handset is a L.M. Ericsson and has some sort of push to talk bar:

[19and41]

The handset shown was a part of one of the first commercially available wire recorders, the Telegraphone.  I have seen color pictures of the full set and it matches right down to the green cloth covered cord.  Here is a black and white picture of the complete set.

http://www.officemuseum.com/MBHT_1917_Telegraphone.jpg

[Sargeguy]

Interesting,  I wonder if there is something about the handset that would make it more suitable for radio telephone use?  Here is another picture:

[DavePEI]

Interesting,  I wonder if there is something about the handset that would make it more suitable for radio telephone use?  Here is another picture:

Might be for tube type radios, but not for crystal radios. The handset would have an impedance of only a few hundred ohms - crystal radios require headphones of 20,000 ohms or greater - the higher the impedance the better.

[19and41]

The device was designed to allow transcription of telephone conversations and it only used the current of the telephone line.  no amplification. 

[DavePEI]

The device was designed to allow transcription of telephone conversations and it only used the current of the telephone line.  no amplification.

Yes, but the point is because it was made for that purpose, it was powered by the line or by batteries, and would have had an impedance of up to 600 ohms. The same can be true of a tube type radio or transceiver.

A crystal radio is powered only by the radio signal, and a telephone handset would draw its output down to nil, and that is why it wouldn't be suited to use with a crystal radio. A crystal radio has no source of power other than the received signal which is in the order of millivolts, and therefore required very high impedance headphones.

Dave

[19and41]

I agree.  I wasn't trying to say it could be used with  a crystal set,  What I meant was that it was remarkable that such a recording device could work in the days before the development of amplifier tubes and that a audible signal could be induced from magnetic influence from a strand of wire.  It wasn't until around 1938 that a vacuum tube wire recorder was available.  The Telegraphone was patented in 1894.