It may be 2 years, but I seem to recall him saying 1 year. Next time he brings along a bunch of them I'll ask him.

Responding to points raised in various posts.

GTC - … I did telephony as a subject with the PMG publication "Telephony II" …

Yes indeed all phone collectors should have a set of Telephony I to Telephony V published from 1935 to 1964. They are still available around the traps and I have several sets. In 1968 was given a set by an ex tech and used them to teach myself telephony. I built a 10-line uniselector PAX from info in these manuals.

GTC - … I also wish I hadn't stripped the 2+4 PMBX …

Again these are still available if you know where to look. I have a few in fair condition and picked up a nice one in Melbourne just last March.

GTC - I suppose those bell motors were designed originally for magneto operation. What did the typical magneto output? It gave a hell of a belt so I seem to recall it was up around the 100 volts mark. And I guess typical cranking speed would have generated about 25 cps?

Actually a long but interesting story. The first telephones used a DC bell but Alex Bell's offsider Thomas Watson, designed both a magneto generator and a matching magneto bell. He had the patent on these and became very comfortable with the royalties he received from Western Electric. Remember that single-wire, earth-return lines were the norm so it was empirically determined that at least 75V was required. Phones that had bells in series rather than a 'bridging' arrangement required up to 110V to work. There were many designs of magneto but something in the range 75 to 100V became the defacto 'standard'. With the gearing necessary to get the required voltage, the frequency averaged out at between 16 to 20Hz. Bell motors were designed to match but the large open frame structure would not have been able to cope with anything much higher. The switchboards of the day were manual and each operator had a magneto that they had to turn to ring the called line. As the size of the boards increased this constant physical effort became a problem. Ringing machines, actually small electric generators, were developed and these were driven continuously by electric or gas fuelled motors. These machines worked at between 15 and 25Hz but later versions had extra windings with interrupter cams to generate service tones at different frequencies. In some cases for party line services divided line ringing was used with special bell motors mechanically tuned to respond only to specific frequencies up to 66Hz. The appropriate ring frequencies were generated by a number of separate windings on a ringing machine. The operator applied the required frequency by selecting one of a set of ring keys on her switchboard panel. Ringing machines were used up until the 1990s.

An alternative ringer was the battery operated pole-changer which was a form of double pole relay that was mechanically tuned to vibrate at about 17Hz and alternatively switched 50V+/- to the line. This gave a 100V square wave which would drive the bell motor. In 1936 when a reliable AC mains supply were available, the sub-cycle ring converter was invented by C. Paul Stocker, an American, and manufactured by his company Lorain Products. This was a type of tuned power transformer that resonated at a third of the frequency of the AC supply. It operated from 105 – 125V or 210 – 240V and put out 85V at either 20Hz or 16-2/3Hz. These were widely used with Automatic Electric PAX. The PMG used these and another version that output 75-90V at 25Hz from 240V 50Hz supply.

Referring specifically to the hand turned four and five bar magnetos found in old wooden wall phones, the Ericsson variety put out about 5W at 80V and the WE or Stromberg-Carlson versions about 6W at 90-100V. The later small Alnico magnetos used in 300/400 Series phones put out about 4W at 750V. In all cases the frequency depended on how fast you turned the handle but would average 17Hz.

GTC - I suppose somebody will design a box to convert the ring voltage to the required voltage and frequency to tinkle the old beauties, but I guess that will need to be mains powered.

Yes, I have already designed but not yet built an interface unit. (Actually it is a modification of a PAX design that I am working on.) It should also be possible to use an old PMBX with a DialGizmo to do the decadic/DTMF conversion.

GTC - Can't say I'm looking forward to all of that junk on a wall in the house; it would be a different proposition if building a new dwelling.

Agreed but I think that finding a suitable space on a wall for the interface unit plus dedicated power point in a new dwelling will be just as difficult judging by some of the places my wife and I have been considering lately. (Baby boomer downsizing exercise.) Remember too that the phone wiring will have to be Cat 3 which you are not likely to find in the average older house.

Brad - I live in a flat and it's not all bad. The copper wire will get used as a draw wire to bring in the fibre through existing conduits between the MDF and each flat.

But will the fibre come out a suitable place for interface unit plus dedicated power point? In my experience wives/Partners/'Significant others' tend to take a dim view of such technology on display.

Brad - The Telstra serviceman was here for about ten minutes. He used the existing spare pair in the phone cable (red and black), connected a socket in the flat and then patched it in on the MDF in the meter room down stairs. He then left and an hour later they enabled the connection at the exchange.

You were extremely lucky to get a real tech who knew what he was doing and whoever was working at the exchange. Last December my elderly mother living in an older suburb of Adelaide lost the use of her phone for twelve days while I was complaining to Telstra that this was due to a recurring line fault as the cable in the street was over 70 years old. (More than 60% of Telstra's line plant is lead-covered, paper-insulated cable at least 60 years old. A lot of the other PVC cables were laid before 1970. Line plant has a design life of 30 years.) Some clown in an overseas call centre told me that his computer said that the line was fine so I had to arrange to have some certified sparky go to the house to fix the fault that must be in the internal wiring. I was going to over to Adelaide anyway so I took tools and test gear. Just listening to the noise on each of the three handsets in the house indicated a line fault with Line A shorted to earth. Line voltage at the point of entry to the premises with internal wiring disconnected was just 18V. After a long call to Telstra on my mobile phone, I was finally told that a tech would come out some time in mid January. I must admit that I was possibly a little rude when I advised the Telstra person that if a tech was not sent within 24 hours, I would be having words to the SA state manager plus the CEO and exactly what I would say to them. The 'tech', actually a contractor to Telstra, arrived the next day but did not understand what an earth fault was. However with a little help from myself, he found that the problem was actually in a pillar at the end of the street where some fool had squashed and cut through the insulation on several jumper wires when putting a metal cover back on the pillar. The case of the pillar is earthed for safety, something that my tech didn't realise. There must have been other subs in the area who had also lost the use of their phone but apparently Telstra had not thought that multiple reports of the same problem in the same area might be indicative of a common fault. I cannot understand why the computerised testing system could not identify a basic earth fault. I have never been employed by Telecom/Telstra or any other telco nor have I done any certification cabling course so it is a rather a worry when I seem to know more about faults in Telstra lines than the tech that is sent to fix them.

Brad - One other thing too, the battery's plastic shell may well have a five year guarantee but what about the battery itself? This particular battery is common in fire alarm panels and I look after seven or eight such panels where I work. We are lucky to get two years out of them.

The telephone system moved to Common Battery exchanges around 1900 for good reasons. Maintaining thousands of batteries at subscribers' premises is labour intensive and expensive. Note however that the onus of battery maintenance has been deftly flicked across to the subscriber; your phone service doesn't work? Did you remember to change the battery? Please refer to the small print under Point 3 on Page 10 of the NBN User Guide. I can just see someone like my 93 year old mother saying to themselves, "Now I must put a 12V SLA battery on my weekly shopping list with some food for the cat too." Having the average subscriber replacing a battery is fraught with danger; now is red positive or negative? How many people will break a lead and/or drop a battery on their foot while trying to get it out of PSU? I would hazard a guess that there will be no end of shonky 'installers' who will 'supply and fit' for a grossly inflated fee.

Correction: The later small Alnico magnetos used in 300/400 Series phones put out about 4W at 75V.

Andrew

Telephony I to Telephony V published from 1935 to 1964. They are still available around the traps and I have several sets.

Well, I'm a definite buyer if you are willing to let a set go, or know somebody who is. I'd really like to bone up on all of the stuff I've forgotten.

I think that finding a suitable space on a wall for the interface unit plus dedicated power point in a new dwelling will be just as difficult judging by some of the places my wife and I have been considering lately. (Baby boomer downsizing exercise.) Remember too that the phone wiring will have to be Cat 3 which you are not likely to find in the average older house.

A mate of mine just gutted and refurbished a two-storey house. He's made the closet space under the stairs into a comms room complete with 19 inch rack and patch board, and run various categories of cables all over the place for phone, internet, security, intercoms, audio and video.

But will the fibre come out a suitable place for interface unit plus dedicated power point?

Probably not. The Commonwealth's insistence on people not using powerboards is going to make a lot of electricians rich. The recommended rate that electricians charge their punters is around $93.00 per hour so anything up to $200.00 could be a fair price per household.

Imagine doing five of those jobs per day...

Re connecting an old phone to a Network Termination Unit, the last requirement is solved. Natcomm sell a Ring Booster that could take the feeble ring signal from the unit and send 100V at 22Hz to your old phone. That will definitely ring a 200, 300 or 400 Series phone and a Bellset No.1 as well. All for $199 (and no I don't have shares in Natcomm). See http://www.natcomm.com.au/au/telephone-line-accessories/ring-booster.html.

Andrew

In response to GTC:

I take it that you were a tech in training at some stage. I am trying to get info on the various PMG training schools for an article on their history.

I do not have a spare complete set of Telephony but I will see what I can find. Perhaps the Administrator would kindly arrange to send each of us the others e-mail address so we can communicate outside this forum.

One curious thing about this series of manuals is that they seem to have been produced on a state-by-state basis at each of the schools and they are all different. For example I have five copies of Telephony II that are the same date, have the same chapter and section headings and are all marked PMG Headquarters Melbourne but each page in each copy is different including the illustrations.

As for a PMBX if you still want one, I may also be able to help there. An alternative if you eBay you might like to have a go at this (but you will have to remove the old wallpaper if you win it).

http://www.ebay.com.au/itm/Telephone-Exchange-PMG-1955-era-/160793466797?pt=LH_DefaultDomain_15&hash=item25700997ad#ht_500wt_1200.

Andrew

Perhaps the Administrator would kindly arrange to send each of us the others e-mail address so we can communicate outside this forum.

Due to privacy restrictions I am unfortunately unable to assist however members can enable the display of their e-mail addresses on their profile page. If this is done and agreeable between members then it's all good.

Relayautomatic:

I really don't have room now for a PMBX, even as a piece of furniture.

I'd settle for a copy of just Telephony II, for starters, as that was our classroom text for the subject. I kept a copy in my bookshelf up until the early 1980's when I had a big book and magazine throwout. I don't think I've seen the other volumes, but I may be forgetting. It's weird to learn that they differed by state, given that it was a national organisation.

I'm happy to talk about that aspect of my early training with you offline. "Unhide" your email address in your member profile and I'll shoot you a message.

Your fibre system sounds similar to the USA Verzion FiOS system. You can get cable TV, phone and high speed internet. Requires a box powered by the mains. And I haven't tried a rotatory phone on it. And our cable TV companies also offer similar cable TV, phone and internet services. So we have two competitors to keep the rates to less than outrageous.

As for running an old ringer, you probably could build an optocoupler circuit with a capacitor in series with the optocoupler, and a backwards diode across the input of that optocoupler. And the optocoupler output could, through an interface circuit, drive a relay to feed whatever AC voltage the ringer needs. But keep that separate from the voice circuits in the phone.

Brad - I live in a flat and it's not all bad. The copper wire will get used as a draw wire to bring in the fibre through existing conduits between the MDF and each flat.

Being a telephone installer in a past life, your suggestion that using the existing "copper wire" as a draw wire for the new cable, might be a little difficult as the draw wire (aka 4wire) is very flexible and is quite easily replaced, but Fibre cable is not. I think it's minimum mean radius is 100mm. As most units/flats are multistory, the conduits carrying the cables coming from the MDF rooms to the respective units usually have a number of bends in them and are sometimes less then a 100mm in radius. Some cables are not in conduits but run through roof spaces, cavity walls, plus under the floors if of an older construction.

Relayautomatic - I am trying to get info on the various PMG training schools for an article on their history.

As far as I can remember in NSW, the main PMG/Telecom/Telstra training schools were.

Strathfield for Technicians.

North Strathfield, Berry St Nth Sydney, Greta and Kenmore for Lineys as I was.

If the minimum raduis is 100mm then yes there'd be trouble all round. Even if the 1/2 inch conduit in use in many installations had elbows on their runs they'd be at most a 20mm radius. This is something us electricians have to worry about too, though not to the same extent.

" In 1968 was given a set by an ex tech and used them to teach myself telephony. I built a 10-line uniselector PAX"

I tried making a gambling machine using these when in High School. Running in 'scan' mode.

And I saw a PBX ~ 100 lines? installed in late 60s in Brisbane Co. that used only uniselectors! (not Strowger units as far as I could see). I wonder if this was common practice or some local "garage" company doing this, it looked like a production product?

You might not be connecting the phone directly to the phone line,
but to a line provided by a digital router, which is connected
to the phone line.
Does it make a difference if the converting device is
outside the router?

Because that phone line is fake.
The phone we have here doesn't work plugged straight to the wall socket.
The router is making your normal phone work over data.

It occurs to me it's the router that would have to support the rotary phone, rather than the phone company.

Hi Guys,
It's experimentation time!
It's possible to make the bell ring with a 12 Volt supply.

I just connected my PCB designed to light pigtail neons using
a 12 Volt supply to my 400 series telephone.

The PCB connects the neons to one side of a transformer,
and a microcontroller is used to generate and switch MOSFETs
at variable frequencies, which in turn present a 12 Volt square waves at the other side of the neon transformers.

At higher frequencies than the eye can perceive, the solenoid just buzzes,
but as the frequency drops to a low that can be perceived by the eye as a flicker,
one bell begins to ring.

Note that the wave I'm producing doesn't have a negative phase compliment, so it would only ring one of the two bells,
just as it only lights one side of the pigtail neons.

The only difference I think would be needed to get a nice ring out of the phone is not a rounder sine wave,
but higher voltage (different transformer ratio) at the correct frequency.
The chip that is producing the frequencies could also detect any old crap at one of it's inputs that is over a threshold voltage to know "the phone line is ringing".

So it should only take two transformers connected 180 degrees out of phase (reverse polarity of one MOSFET),
and provide one MOSFET with the inverted phase of the synthesised waveform.

Although the input is an absolute square wave, I haven't
looked at how that wave is transferred through the transformer.
It could be rounding it off somewhat.