As advised by Monochrome625, your phone is a PMG 400AT that was introduced into service in 1958 but the type was made until 1962 and they were used until the early 1980s. The 400AT was based on the British GEC model 1000 and the BPO Tele 700 (which was a limited trial prior to the introduction of the plastic case Tele 706). It was designed to work on long or high resistance lines up to 1000 ohms. In the 1950s there was an expansion of suburban housing and the lines to the exchanges had to be much longer than the three to five miles that had previously been the case. The earlier 300 series phones did not work very well on longer lines but the 400AT had a better design of induction coil (audio transformer) and a more efficient 4T rocking-armature receiver. The 400AT was made by AWA and STC in Australia and by Ericsson (ETL), GEC and ATM in Britain. The AWA/STC version is known as the APO assembly and has all the internal parts except the dial mounted on a single base-plate. The British made versions are known as the BPO assembly and had the components mounted on an internal chassis. If you look at the bottom of your phone it should have one or more letters followed by two digits. The letter/s is the manufacturers’ code and the numbers the year made. So for example ‘E 60’ is Ericsson 1960, ‘C 59’ is GEC 1959, ‘H 59’ is ATM 1959 and ‘AWA 61’ is AWA 1961. If the phone has been rebuilt at the PMG workshops it may have a paper sticker over the original markings. The earlier 400AT were fitted with an all metal No 12 dial but later phones had a No 12 dial with a black plastic fingerplate and the number ring was black with silver numbers. Rebuilt phones were often fitted with a black plastic No 21 dial. The early 400AT with the metal fingerplate No 12 dial had the dial card with letters (A B F J L M U W X Y) but the later plastic fingerplate and No 21 dials did not have letters. The use of letters in telephone numbers was discontinued by the PMG from 1960.

These links will give you more info on the 400AT and its origin. (The phones shown with the brick wall in the background are mine.) Note that Bob has confused the Serial/Item number with the PMG type number, they are all PMG 400AT (Automatic Table) but the serial/item number was different depending on the manufacturer and the supply contract.

http://www.britishtelephones.com/aus/400type.htm
http://www.britishtelephones.com/t700.htm
http://www.britishtelephones.com/dial1.htm
http://www.britishtelephones.com/dial21.htm

Reprints of dial cards are available from the Australasian Telephone Collectors Society (of which I am a member). http://www.telephonecollecting.org/books_for_sale.html

If you want to use DTMF dialling without modifying your phone I would suggest a Dialgizmo (http://www.dialgizmo.com/) which I have found works very well. I have not tried using an old phone with a Cisco router but I doubt that it would accept decadic dialling. For the line feed you need a DC voltage of 24V to 48V and for ringing 75-90V at 17-30Hz. If the router is not recognising the phone as off-hook it could be the resistance of the carbon mic is too high and needs replacing.

Andrew

Welcome back Relayautomatic.

Hello too GTC. I thought that I was the only one up late. I am still looking for a Telephony II for you. Andrew

I'm doing my own DTMF solution though.
Well already done really, but I'm just afraid to use it!

I went to my first ham meet, and someone had an idea.
Connect the earpiece to the dial when a number is dialled
so the user still hears pulse dialling while tones are sent down the line.
That's creative.

Mine has both a stamp and a sticker label:

S.T.C 59 P.M.G. S1/401

and the paper sticker:
P.W.B. T 370 Assembled by one signature and Tested by another.

So I still made the 50's
Does that mean the dial started out one model and was changed later by the company?
That I could settle for.

Balls to any digital solution out there,
Rotatone is one hours work.
I can do much better when I know the detail.

This arrived yesterday, and is interesting:
http://explodingthephone.com
In fact, I already recommend it, but I don't think it will
be helpful in terms of technical information.
I'm interested in Phreaking (history), but not in breaking the law so much myself.

After looking at this I'm more confused:
http://www.britishtelephones.com/aus/400type.htm
Mine has air vents that I was calling "ringer holes".
They only exist on a different model altogether.

I am still looking for a Telephony II for you

Many thanks.

As I hadn't seen you post for a long time I thought perhaps you had forgotten your password (The password recovery function had not been working for some, so I got locked out myself for a while!)

Art,

I'm not sure I understand what you are trying to achieve when you say a DTMF solution. Do you mean generating the corresponding DTMF tones when you dial a number? If so have you seen this link? (http://boris0.blogspot.com.au/2013/09/rotary-dial-for-digital-age.html)

In the 400AT circuit the second set of dial contacts shorted out the receiver so that the caller did not hear the clicks. This was a form of protection against acoustic shock.

S.T.C 59 P.M.G. S1/401 translates to Standard Telephones & Cables (Australia), 1959, Postmaster Generals Department, Serial Number 1, Item number 401 [Note that the 401 item number does not mean that the phone is a 401AT.]

The sticker with P.W.B. T 370 shows that the phone was rebuilt at the Postal Workshops Brisbane probably in the 1970s. Sometimes there is a date on the sticker but often it is illegible. It is most likely that the plastic No 21 dial was fitted during the rebuild if the original No 12 was damaged. Generally the recovered phones were stripped down into their various parts and then anything that was worn or damaged was replaced with parts from other recovered phones. So many phones became a mix of original, refurbished and new parts. Have a look inside the bakelite case between the two plungers and see if there is a moulding mark. If it is the original case there should be the letters STC in a circle. If it has PMG, PW or MK then it is a replacement. The phone is still a genuine 400AT all the same. (Just as a vintage Rolls Royce does not become non-genuine just because it has new set of spark plugs fitted.)

The vents in the case were to let the bells be heard but also served as a lifting point for the phone. Ericsson made phones had silver coloured alloy vents and GEC made phones had black metal vents. Both of these versions also had holes in the metal cover underneath the case. The AWA made phones did not have vents initially but later versions had black plastic. The STC made phones had black plastic vents. The plastic vents were easily broken and rebuilt phones with vented cases often had solid plastic plugs stuck into the holes which rather defeated the purpose of the vents.

Also be aware that the 400AT came in black or ivory but only Ericsson made the ivory case and these phones always had a metal No 12 dial. The pics on the British Telephones site show the various combinations.

Concerning the book, I have not read it but a lot of what passes for history on the Web and in such books is wrong and/or tells only the Bell/AT&T version of the story. The use of audio tones to control trunk switching was called VF signalling and had been around since 1940. Bell/AT&T used their own version which was not secure while everybody else used a different version that never had problems as far as I know. It was possible to make calls over trunks between exchanges on the PMG system if you knew the codes but you usually needed access to the exchange equipment.

As for breaking the law, there is no law as such only regulations. Equipment has to be 'certified' by AUSTEL or now ACMA. Non-certified equipment is not permitted to be connected. (See some of my other posts on certification.) However certification has become a joke with the amount of non-compliant equipment everywhere. The original idea was mainly for electrical safety so that failure of equipment would not put 230V onto a phone line which is quite a valid reason. However a lot of PMG/Telecom phones would not have passed certification if they had been tested. Most US made equipment would not have passed either but try banning its use. As for most Chinese made equipment, no chance if a production unit was tested rather than the 'type sample' that may have been submitted. Referring specifically to your 400AT; does it have exposed metal parts? If yes then it fails certification. (I know from testing that the dial and the handset would fail the 500V insulation test. If you have a megger give it a try!) However I have not heard of any individual being nabbed unless they did something particularly stupid and dangerous. I do know that an Actew/AGL crew managed to interconnect a high voltage underground line with a phone cable while digging up a gas main at the end of my street. This resulted in a fire in the exchange MDF because Telecom no longer fits fuses and arrestors to save on maintenance costs. Does this modification invalidate the type certification on the exchange equipment?

Andrew

Ok, yes I'm happy with the differences in the phone if a company did it,
but will look out for an original dial since I do like the chrome looking ones.

I want to do a DTMF solution yes, I'm going to have to end up wrecking a cheap corded Big W phone for the DTMF encoder chip since Jaycar only sell the decoder chip.
At the moment I'm doing the tones with microcontroller software,
they are square wave and harsh although the exchange does understand them.

I want to make the whole thing myself.

I've done that kind of thing, but it's still not good enough
for everyone or to teach me anything.
It needs to be an intermediate thing between the rotary phone and the IP router / phone line, connected only to each device by the ring and tip pair.
That is a thing you could send to someone, and not modify a phone.

Some time, some guys wanted to make a phone ring,
and since the mains in their country was much closer to
the voltage and wave required to make a phone ring,
they thought it feasible to plug it into a mains socket to test the ringer.
When the phone rang, one of the guys picked up the handset.

So I kinda have to take this up when there are no distractions
We can't get DTMF encoder chips locally, only decoders from Jaycar.
I'm hoping a $20 Big W phone has the chip in it.

Is that yours? because it is impressive to get DTMF out of a chip driven with a 4MHz crystal.
That's the reason I want a dedicated DTMF chip,
the tones I'm producing at 20MHz are good enough for the exchange, but aren't pleasant to hear.

First music video, about a bunch of other firsts by Bell Labs.

http://www.youtube.com/watch?v=Rw80b6gelR0.

Anyone got a schematic for this one please?
I think there's meant to be one on the base, but this one is missing.
Cheers, Brek.

What exactly is the schematic for?

Hi Monochrome, I think we agreed it's PMG 400AT

Yes Art.

I can shoot you over the schematic when I get home tonight.

Cheers.