Phone wiring confusion

[tonyelectric]

The ringing current comes along the same circuit as everything else, between 2 & 5, it is as the explanation says superimposed over the idle on hook circuit, there are only two wires in the system, Tip & Ring, A & B, Tip or A being earth the other the line.

 

[securespark]

Can this be moved?

I think it will help some of those using the Telephone Forum.

 

[Lectrician]

The ringing current comes along the same circuit as everything else, between 2 & 5, it is as the explanation says superimposed over the idle on hook circuit, there are only two wires in the system, Tip & Ring, A & B, Tip or A being earth the other the line.

Yes, but my post is still correct - there is only a single pair from the exchange to the NTE, but from there onwards you should have a pair plus one. To be 100% correct you should also use the other core from the pair you use for the ringer for terminal 4, it has no purpose, but keeps all the pairs together.

 

[bernardgreen]

Yes, but my post is still correct - there is only a single pair from the exchange to the NTE, but from there onwards you should have a pair plus one. To be 100% correct you should also use the other core from the pair you use for the ringer for terminal 4, it has no purpose, but keeps all the pairs together.

Lectrician is correct

The plug in system wiring was designed to have one capacitor at the master socket providing the AC voltage to wire 3. All telephones should then have their bell ( or sounder ) connected between wires 3 and 5.

This provided the exchange with a known capacity to measure when line testing and most importantly it limited the amount of ring current a line could take from the exchange. Phones that do not use wire 3 but have instead their own "bell" capacitor add more capacitance into the ringing circuit and this can increase the amount of ring current to the point that the exchange sees enough current to consider the phone has been answered and "ring trip" occurs. Modern electronic exchanges have been designed to be more discriminating between AC peak current and steady state DC. But too many phones with own "bell" capacitors will still increase the risk of ring trips. Yes I know the micro filters have an extra "bell" capacitor in them, a necessary compromise in order to roll out broad band as an overlay onto a wiring system not designed for it.

The best option is always to separate ADSL ( broad band ) signals from the phone signals at the master socket ( NTE 5 with ADSL filtered faceplate ) and have separate cabling for phones and ADSL.

 

[Chri5]

you should also use the other core from the pair you use for the ringer for terminal 4, it has no purpose, but keeps all the pairs together.

That is the earth terminal for EBR- earth break recall. Which is used to transfer or park calls on a PABX system with EBR.

Since the 90's most systems used the TBR- time break recall, although the USA used TBR long before the UK. Due to MF dial phones

 

[bernardgreen]

Best document ever on phones has to be the Bell System Practices, American book c1930s - 1984, the '84 edition covers almost everything, the US got tone dialling in about '62 and were way ahead of the GPO so the BSP is about up to date for us now

Forgive if I disgree there. The best book on telephones is Atkinsons.

The US got tone dialling before the UK because tone dialling was needed to overcome the problems that the American telephone "network" had created for itself. In the UK all telephone exchanges similar in standard and were interlinkable. Pulse dialling would take you quite a long way across several tandem ( transit ) exchanges that linked your exchange to the exchange of the person you were calling.

In the US it was very different. Some towns had two exchanges owned by different private companies and using different technology. Subscribers could only call people whose phone was on the same exchange as they were. Some people had two phones. Interconnect between the two exchanges with loop dis-connect was not possible without installing new equipment ( trunk ciruits with signalling ) that the exchange owners would not pay for. If they did they would lose customers.

Local and federal pressure was put on these private companies to permit interconnect

Tone dialling made such interconnection possible. In simple terms you phoned the other exchange which answered the call as if it was an ordinary call. It was not a truck circuit with signalling so loop disconnect dialling between exchanges was not possible. At first an operator took the number you wanted and dialled it for you. Then the operator was replaced with a tone to pulse convertor. With a dial tone from that exchange you then dialled the number you wanted in that exchange but it had to be in tone format.

 

[Chri5]

According to legend, Almon Strowger, (an undertaker) was motivated to invent an automatic telephone exchange after having difficulties with the local telephone operators, where the wife of a competitor was one of them. He was said to be convinced that she, as one of the manual telephone exchange operators was sending calls "to the undertaker" to her husband, who ran a competing undertaker business.

He first conceived his invention in 1888, and patented the automatic telephone exchange in 1891. It is reported that he initially constructed a model of his invention from a round collar box and some straight pins.

 

[tonyelectric]

The strowger story is indeed true to my knowledge, I believe Elisha Otis was also an undertaker and developed the safety elevator to move coffins. Dorr Felt made the prototype for the comptometer from a macaroni box and sticks - went on to be on of the most successful products.

The American telephone system whilst not perfect was streets ahead of us over here, mainly due to the AT&T companies huge investments in R&D, although there were many regional companies they were mainly controlled by either AT&T or General Telephone & Electronics and all used the infrastructure provided by the Bell System, the DNO if you will of the US system until 1984 when the monopoly was ended.

Interestingly the superb 2500 desk phone (which is still produced after 40+ years and which we supply to business customers here) design was owned by Western Electric, a subsidiary of Bell who also owned STC who made the, by comparison cr*ppy 700 series for GPO/BT, the yanks kept the best for themselves.

And regardless of different models the 2500 only uses 2 wires, there is a ringing cap on the network between terminals A & K which sits in circuit between a high impedance and low impedance coil for the ringer. The supplied leads for 2500 sets have only 2 cores unless you opt for the planset that has a 50 core lead, or director with 100core lead

 

[Lectrician]

you should also use the other core from the pair you use for the ringer for terminal 4, it has no purpose, but keeps all the pairs together.

That is the earth terminal for EBR- earth break recall. Which is used to transfer or park calls on a PABX system with EBR.

Since the 90's most systems used the TBR- time break recall, although the USA used TBR long before the UK. Due to MF dial phones

Yes, but we are talking a standard PSTN line here.

If you want to descibe every possible combination, we could start listing off when the 1+6 get used, when 3+4 are used for data for featurephones, which can cause issues when pillocks change the secondary for a master, or swap a featurephone for an SLT and wonder why it wont ring.

PBX's that still use earth recall are few and far between - most have been long resigned to the skip.

 

[Chri5]

There's still several 1000's of SG's (Mitel SX 200) Regents (Mitel sx200), Kinsmans (Sx20) and SX50's

All the analogue / POT's were EBR in the UK

I spent 80's and most of the 90's fitting them !


Lectrician- you post suggests you think I was having a dig, I wasn't- I was explaining that the pin 4 does have a purpose (all be it in commercial world), when you said it didn't.

Nearly all cablers used to wire 2 pair terminated (2,5,3 and 4) at the LJU, back at the block wire point (krone BC201, or even 237's in a BC300) the extra termination were not made unless EBR or a key phone set requiring 2 pair working (voice / data).

 

[Lectrician]

OK, fair enough - it's just this thread was about a standard PSTN line.

Funnily enough I took out a kingsman only this week just gone.....

Not seen many PBX's of this sort of age still in situ myself though.

I mainly deal with BT Versatility and Insp/Path, Panasonics, and the NEC XN120 and a little bit with the Aspire.

 

[Taylortwocities]

There's still several 1000's of SG's (Mitel SX 200) Regents (Mitel sx200), Kinsmans (Sx20) and SX50's
.

Ahh yes, but how many of the old IBM 3750s are still running I wonder?? I can't quite remember, was that the first private SPC exchange?

 

[Chri5]

IBM3750's god that's a blast from the past. There were 5 or 6 dotted around London Bridge (my old BT patch) massive battery rooms and 10 x large washing machine sized units (and disc storage) for modest sized firms.

When the shrunk down SPC's arrived salesman made sales by giving a business case for saving footprint space in the buildings. 600 sq ft for old, 60 sq ft for new.

It was also an era of lock in leases where Co's like TR sold systems on 20 year non exit leases

 

[bernardgreen]

You certainly respond very quickly, you advert was posted less than 8 months after the original question was posted.

 

[Taylortwocities]

My friend used Triton for his phone system.
They made such a hash of things he had to get another company in to do the job properly.

no advertising here,either