[QuadList] Patch cables/bays (Was ...some useful info from BAVC...)

[COURYHOUSE at aol.com]

Again Ted well done!  I will check on this in  the morning when I am out  
at the building.
again many thanks  Ed



 
In a message dated 7/12/2009 11:08:05 P.M. US Mountain Standard Time,  
ted at quadvideotapegroup.com writes:

Hi,  Ed,   


Glad you found the links useful.



 
On Jul 12, 2009, at 10:25 PM, _COURYHOUSE at aol.com_ 
(mailto:COURYHOUSE at aol.com)  wrote:


Seeing one photograph of  racks reminds  me...  I have the rack part of the 
video patch bay but do not have any  cables to plug in!  It would be nice 
to set everything up this  way...  does anyone have any extras?




You may be easily able to tell what you have by looking at the side of  the 
jacks and then Google the part numbers.  Do that first before jamming  a 
patch cord in one.  The wrong size will either not fit or cause  damage.



This ADC document 
_http://www.adc.com/us/en/Library/Literature/106085AE.pdf_ (http://www.adc.com/us/en/Library/Literature/106085AE.pdf) 
explains the differences and the damage that can be caused to an RCA  style 
jack if you try using a WECO (Western Electric) style patch cord.


So, you need to know whether your panel has: 


WECO or RCA
75 ohm or 50 ohm (You need 75 for video)
Terminating or non-terminating
Normaled or single jack "straight-through"


It might have a mix of patch styles.  Look closely for part numbers,  and 
if necessary carefully remove the jacks from the panel to  investigate.


Aside from the physical differences, the ADC doc. outlines some problems  
using standard WECO jacks and patch cords with Serial Digital signals.  


ADC has a special patch cable that allows use of existing WECO jacks with  
SDI signals without  an impedance problem leading to excessive bit error  
rates.


Like water flowing downhill, patch bays are usually set up so that if you  
have—say— the output of a VTR intended to go to a switcher input, the 
source  output goes to the top jack and the destination input is fed from the 
lower  jack, right underneath.  


This allows the use of "patch plugs" to direct the signal if "Straight  
Through" jacks are used in the jack field.


A straight-through jack requires a patch cable to work. It may be  
terminating (adds a 75 ohm resistor across the circuit when there is no patch  cord 
inserted) or non-terminating, which requires a termination at the patch  bay 
if the circuit is active.


A "Normaled" jack allows video from the rear upper jack connection to  flow 
through to the rear lower jack connection without a patch cable in place.  
Most patch bays I've run into are "normaled."  


It makes life a lot easier and requires the use of a patch only if  there's 
something un-usual going on.  Say, patching around a bad device,  or 
sending a source to a destination that's not available without the  patch.


Hope this is helpful.


Ted



 
 
 

Ted  Langdell
Secretary
Skype:  TedLangdell
e-mail: _ted at quadvideotapegroup.com_ (mailto:ted at quadvideotapegroup.com) 








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