[GreenKeys] Re Patch panel details

[kf9nz at juno.com]

                There's a little more to it than just a ground.   The
sleeve wire was used as the busy test.  The Operator would touch the tip
of a calling cord to the sleeve, which was exposed.  If the line or trunk
was busy, she (almost always a she) would hear a click in the headset.  
As dial switching was developed, the sleeve wire continued to be the busy
test by means of which trunks could be automatically tested.  The sleeve
was the holding circuit for established calls.  Intra-office trunks were
3 wire -usually.

                As for tip-sleeve jacks, they were more than one type of
spring pile-up.  On the RR we used them for both telephone and telegraph
(rtty=printing telegraph) circuits.   Most railroad wayside telephone
circuits  were open wire construction with drops into all wayside offices
(stations or depots).  The telephones were local battery phones, so there
was no "busy" indication.   There were a couple of different types of
signalling such as  3 1/2 cycle selectors, and 20 cycle code.  The jacks
on these circuits were either  a simple T-S  jack to bridge on the line,
or  "normal" jacks with two normally closed springs that allowed office
equipment to be patched to different circuits.
                The telegraph jacks were either "loop" jacks that allowed
a meter or instrument to be added into the loop, or "set" jacks that cut
an instrument out of its normal loop while closing the rest of the loop,
allowing it to be patched into a different loop, or whatever.
                More than you wanted to know about jacks and plugs?

Frankf9nz

On Thu, 8 Jul 2004 17:17:13 -0400 (EDT) John Lawson <jpl15 at panix.com>
writes:
> 
> 
> On Thu, 8 Jul 2004, Roy Morgan wrote:
> 
> > Greenkeyers,
> >
> >
> > What was the use of the TRS-type jacks, audio/telephone circuits?
> >
> 
> 
>    In audio / telephone work, TRS plugs and jacks are used where a 
> balanced 
> circuit is to be patched - one side goes thru the 'tip' and one side 
> goes 
> thru the 'ring' - both of which are insulated from the 'sleeve', 
> which is 
> generally frame or earth ground.
> 
>    A secondary use of TRS jacks/plugs is where a live circuit must 
> be 
> interrupted with an 'insert' circuit, again w/out grounding either 
> of the 
> signal lines.
> 
>   Cheers
> 
> John  KB6SCO
> 
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> 
> 

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