[VoIP] Channel Bank on Ebay [not mine] and E&M

[Steph Kerman]

John Novack wrote:
> Correct.
> The best reference I have found on line, though by no means complete, 
> and I have not checked it completely for accuracy, is here:
>
> http://www.arcelect.com/RJ_Jack_Glossary.htm
However it does not show the 4-line RJ-61 used on some KSU-less 4-line 
key systems.  Various commercial references I've seen for the RJ-61 show 
the polarity of the 4th line with either of the 2 possibilities.  The 
first 3 lines are shown with consistent polarity among all the refs I've 
seen, complying with the RJ-25, which is T3-T2-R1-(center line)-T1-R2-R3 
across the jack.  The inconsistency of flipping the polarity between 
lines 1 and 2 apparently results from the goofy assignments of lead 
colors to the jack when the jack design was initially standardized, one 
of many blunders IMO.
> Mentioned is the RJ-71 which is SIMILAR to what I was referencing in 
> my earlier posting, and perhaps one with built in contacts was never 
> built.
Referring back to your earlier comments, I've certainly seen 66 blocks, 
both 66Ms and 66Bs, that were connectorized with a 57-series plug or 
connector on the side.  I've never heard of them being referred to as a 
"66 style jack" though.  I've also never seen equipment nor reference to 
a "closed circuit" 57-series plug or socket, one which established 
continuity between pairs of contacts when unmated.  I found the RJ-71 in 
my 1980 Registration Manual.  Indeed, *that* is the one used in 
apartment house lobby door answering systems, not an RJ-20 series I 
mentioned earlier.  Those RJ-20-series flavors (21-24) which use 25-pair 
connecting devices are strictly bridged T&R connections, with or without 
A leads. 

Considering the choice of contact positions on the plug in RJ-71 for 
each through-connection (26-1, 27-2, etc), where each circuit enters on 
one row and exits on the directly opposite contact, that choice 
certainly was the best one to make possible the design of a closed 
circuit "connector" as well as facilitating hand-wiring of the jumper 
plugs.  I've seen PCB edge connectors designed to close a circuit 
between the contacts on opposites sides when the PC board was removed 
but that's an unusual case.

As an aside to this already off-topic thread about misappropriation of 
technical terms, the Bell System itself was not guilt-free.  Use of the 
term "connector" itself is an institutionalized misuse by the Bell 
System of a pre-existing and well understood term.  In the electronics 
industry, and probably elsewhere in the Bell System, "connector" was 
used as a genderless term for a plug (male) *or* socket/jack (female).  
When they adopted the use of 57-series connectors: plugs (on equipment, 
generally: telephone set cords and 584 panels) and sockets (on the ends 
of cables), they chose to use the word "connector" instead of "socket" 
to refer to the female device.  I suspect that if I went looking for 
references to other types of plugs and sockets in other BSP subject 
areas, I'd find the term "connector" being used to denote a connecting 
device of either (non-specific) gender, inconsistent with the way they 
chose to use the term in relation to KTS equipment.
> They also do not specify in all cases the keyed/unkeyed plug, though 
> these days the keyed plug is seldom seen in use.
AFAIK the keyed plug was limited to use with true RJ-40-series interface 
jacks in which the transmit level of the modem was maximized under 
control of the resistor in the jack, installed there by the telco, 
presumably after measuring the loop loss.  This may have made sense in 
the days when the 212 1200 BPS modem was state of the art for dial up 
data transmission, to squeeze ever last dB of S/N ratio out of the 
connection but it pretty much fell by the wayside due to the complexity 
of administration once modem mfrs decided it was easier to simply adhere 
to a slightly lower default maximum transmission level and sacrifice the 
marginal improvement in performance that might have come by using the 
RJ-40 series connections.

Steph
> Steph Kerman wrote:
>> If I'm not mistaken, the misuse of RJ45 in the way you cited is doubly 
>> incorrect since it's used to refer to an unkeyed plug and jack whereas 
>> the RJ40 series jacks in fact use the keyed plug and jack.
>>
>> John Novack wrote:
>>   
>>     
>>> Understood, but there are many CORRECT references available to the 
>>> world, as well as recent postings to this list, way off topic though it
>>> might be!
>>> The most frequent abusers of ( this ) terminology are those in parts 
>>> of the computer field.
>>> Again, RJ45 references an application and a wiring pattern that 
>>> doesn't even apply to Ethernet T568A or B.
>>> An RJ45 is a 2 wire circuit, using pins 4&5.
>>> Thy both just HAPPEN to use the 8 position modular plug and jack, 
>>> which is also used for many electronic stations off of Key and PBX, 
>>> Merlin, Legend and Horizon to name just 3 in the US.
>>>
>>> John Novack
>>> windmill wrote:
>>>     
>>>       
>>>> John,
>>>>
>>>> Well I'm a telephone type, but a UK telephone type of some 37 years 
>>>> experience now, and RJ doesn't have the relevance here that it does 
>>>> in North America.
>>>>       
>>>>         
>>>   
>>>