What does all the jargon mean?
To the novice collector, the various ,historical telephone technologies and the jargon used may be a little difficult to understand. The following topics are discussed below:
Contents
To the novice collector, the various ,historical telephone technologies and the jargon used may be a little difficult to understand. The following topics are discussed below:
Contents
- Manual and automatic exchanges
- Public Switched Telephone Network (PSTN)
- PBX/PABX.
- Automatic telephony tones
- CAN (and NBN)
- MDFs, cabinets, pillar and cable.
- Local battery/magneto/party lines
- Single wire lines
- Battery ringing telephones
- Central battery
- Analogue and digital telephony
- Mobile telephony
- NBN.
The first telephones
Some controversy surrounds the claims about who was the inventor of the telephone (here) but Alexander Graeme Bell patented and sold the first known practical telephones in 1877. His telephone was a very simple device that served as both a transmitter and receiver and was "sound powered", it did not use any electrical source such as a battery. It consisted of a voice diaphragm, permanent horseshoe magnet and a pair of insulated wire coils. Voice vibrating the diaphragm varied the magnetic field which in turn induced electric current into the coils. This generated a varying electrical signal, containing the voice information, that could be transmitted down a line. The voice was recreated at the other end when the varying current created a varying magnetic field that "drove" the diaphragm. The phones had limited transmission performance and were generally operated as "point-to-point" services, although rudimentary switched networks appeared a year or so later. Some images of Bell style phones can be viewed here and here .
The principle of Bell's phone is virtually the same as a typical electromagnetic telephone receiver. Similarly, one of these receivers will work in reverse as a rudimentary transmitter. It has been unkindly suggested that Bell really only invented a receiver that, coincidentally, operated as a form of transmitter.
Bell's telephone was soon made obsolete by the local battery/magneto telephone. A principle that persisted for more than 100 years. More information on LB/magneto systems here and here
Some controversy surrounds the claims about who was the inventor of the telephone (here) but Alexander Graeme Bell patented and sold the first known practical telephones in 1877. His telephone was a very simple device that served as both a transmitter and receiver and was "sound powered", it did not use any electrical source such as a battery. It consisted of a voice diaphragm, permanent horseshoe magnet and a pair of insulated wire coils. Voice vibrating the diaphragm varied the magnetic field which in turn induced electric current into the coils. This generated a varying electrical signal, containing the voice information, that could be transmitted down a line. The voice was recreated at the other end when the varying current created a varying magnetic field that "drove" the diaphragm. The phones had limited transmission performance and were generally operated as "point-to-point" services, although rudimentary switched networks appeared a year or so later. Some images of Bell style phones can be viewed here and here .
The principle of Bell's phone is virtually the same as a typical electromagnetic telephone receiver. Similarly, one of these receivers will work in reverse as a rudimentary transmitter. It has been unkindly suggested that Bell really only invented a receiver that, coincidentally, operated as a form of transmitter.
Bell's telephone was soon made obsolete by the local battery/magneto telephone. A principle that persisted for more than 100 years. More information on LB/magneto systems here and here
Telephone Exchanges
Manual exchanges:
At the customer's request the telephonist performed the connections by hand at the switchboard.
The 1937 image below is of a small Australian semi-rural manual exchange (Kalamunda - about 25 km east of Perth WA) - typical of the first half of the 20th century. The telephonist (believed to be Miss Doreen Penrose) is sitting at the manual switchboard and cable distribution frames are visible in the background. Left rear is what appears to be a small "pyramid" cordless switchboard (example below). There was a small exchange in Kalamunda from 1911 -1921 prior to the construction of this post office. It is even possible that this was it and simply relocated to the new premises. There was a forestry party-line (see below) in the area to the east at the time - it may also be part of that (Party lines discussed below).
Manual exchanges:
At the customer's request the telephonist performed the connections by hand at the switchboard.
The 1937 image below is of a small Australian semi-rural manual exchange (Kalamunda - about 25 km east of Perth WA) - typical of the first half of the 20th century. The telephonist (believed to be Miss Doreen Penrose) is sitting at the manual switchboard and cable distribution frames are visible in the background. Left rear is what appears to be a small "pyramid" cordless switchboard (example below). There was a small exchange in Kalamunda from 1911 -1921 prior to the construction of this post office. It is even possible that this was it and simply relocated to the new premises. There was a forestry party-line (see below) in the area to the east at the time - it may also be part of that (Party lines discussed below).
That also ties in with my family story. My grandfather, Peter Dobric's property at Piesse Brook (Kalamunda area) in the 1930s was attached to the above-mentioned party line and his code was "two shorts and a long ring" (Morse code for the letter "U").
The image at left, of a turn-of-the-century small cordless switchboard, is from a 1913 Ericsson catalogue. It bears a striking resemblance to the item described above. More background about Kalamunda's exchange history can be seen here. The last public manual exchanges closed in Western Australia (Tenindewa) in April 1985 and Australia (Wanaaring NSW) December 1991. |
Automatic exchanges:
Manual exchanges were progressively replaced by automatic switching from 1912 in Australia. Although both technologies existed concurrently in the Australian network for most of the 20th century. Connections are/were made over a (mostly) copper wire network and switched automatically by electrical/electronic equipment in the telephone exchanges. Dial pulses or tones from the telephone signal the required number to the exchanges.
Public Switched Telephone Network PSTN
The automatic telephone system is known (worldwide) as the PSTN (Public Switched Telephone Network) and sometimes nicknamed POTS (Plain Old Telephone System!).
Analogue exchanges
The original automatic exchanges used analogue transmission and electro-mechanical switching technologies and dialling signals were originally DC electrical pulses from a rotary dial. This method is referred to as impulse, decadic, loop disconnect or rotary dialling depending on whose book you read.
Digital exchanges
The last generation of exchanges in the PSTN are/were electronic, using digital switching techniques similar to modern computers. The customer's phone uses DTMF tones from a keypad to signal the exchange, although, prior to NBN telephony, many Australian digital exchanges still accepted the obsolete dial impulses. The Australian PSTN will mostly be closed by 2022 - superseded by NBN/internet. After that time this information will be of historical interest only.
Manual exchanges were progressively replaced by automatic switching from 1912 in Australia. Although both technologies existed concurrently in the Australian network for most of the 20th century. Connections are/were made over a (mostly) copper wire network and switched automatically by electrical/electronic equipment in the telephone exchanges. Dial pulses or tones from the telephone signal the required number to the exchanges.
Public Switched Telephone Network PSTN
The automatic telephone system is known (worldwide) as the PSTN (Public Switched Telephone Network) and sometimes nicknamed POTS (Plain Old Telephone System!).
Analogue exchanges
The original automatic exchanges used analogue transmission and electro-mechanical switching technologies and dialling signals were originally DC electrical pulses from a rotary dial. This method is referred to as impulse, decadic, loop disconnect or rotary dialling depending on whose book you read.
Digital exchanges
The last generation of exchanges in the PSTN are/were electronic, using digital switching techniques similar to modern computers. The customer's phone uses DTMF tones from a keypad to signal the exchange, although, prior to NBN telephony, many Australian digital exchanges still accepted the obsolete dial impulses. The Australian PSTN will mostly be closed by 2022 - superseded by NBN/internet. After that time this information will be of historical interest only.
Analogue telephones
It is interesting to note that Australia's telephone exchanges had moved from analogue transmission and switching to digital technology by the end of the 20th century but the customers' telephones remained analogue devices, presumably to retain "backward compatibility" and obviate the need to replace millions of telephone instruments. The solution was to provide analogue to digital conversion at the customer interface in the new digital exchanges. This has flowed on to today where typical NBN modems provide an analogue telephone port so customers can continue to use their traditional telephone, even though the transmission path is now digital from end to end.
It is interesting to note that Australia's telephone exchanges had moved from analogue transmission and switching to digital technology by the end of the 20th century but the customers' telephones remained analogue devices, presumably to retain "backward compatibility" and obviate the need to replace millions of telephone instruments. The solution was to provide analogue to digital conversion at the customer interface in the new digital exchanges. This has flowed on to today where typical NBN modems provide an analogue telephone port so customers can continue to use their traditional telephone, even though the transmission path is now digital from end to end.
Automatic telephony tones
To advise users of the progress of a call, a range of standard tones were used. This Youtube clip gives a very clear rendition of tones from around 1950. https://www.youtube.com/watch?v=223k6xxIkbo
It is British Post Office but virtually the same as Australian. In fact, the voice is possibly of the Australian actor Gordon Gow who worked in the UK in the 1950s. Gordon was the first voice of the speaking clock here installed in Victoria and NSW in 1954.
To advise users of the progress of a call, a range of standard tones were used. This Youtube clip gives a very clear rendition of tones from around 1950. https://www.youtube.com/watch?v=223k6xxIkbo
It is British Post Office but virtually the same as Australian. In fact, the voice is possibly of the Australian actor Gordon Gow who worked in the UK in the 1950s. Gordon was the first voice of the speaking clock here installed in Victoria and NSW in 1954.
PBX and PABX
The terms private manual branch exchange (PMBX), private automatic branch exchange (PABX) and private branch exchange (PBX), refer to privately owned telephone switching networks used to manage telephony in businesses, college campuses etc. Historically they were based on manual switchboards but automatic systems soon became popular. Typically they consisted of centralised switching equipment, a number of telephone "extensions" and some "exchange lines" connected to the public network. Sizes varied enormously from small systems with a few extensions through to large systems comparable to a small PSTN exchange. Since their inception in the early 20th century they have become progressively more sophisticated and the term "PBX" now tends to cover all types. An associated topic, Digital PBX, is introduced here.
There is a good description of PBX/business systems systems and their history at:
https://en.wikipedia.org/wiki/Business_telephone_system
The Customer Access Network (CAN)
The CAN is an acronym that regularly pops up. This is/was the copper wire network between customers and their local exchange. It comprises/ed a network of pair cables and cross-connect units called MDFs (main distribution frames), cabinets and pillars. The MDF is the equipment in buildings that terminates cables and allows cross-connections. MDFs are located at both the telephone exchanges and in larger customer premises. More information on the technical aspects of telephone cables etc. can be found here.
The CAN is of particular interest today. The original intention was to wholly replace it with an optical fibre/digital transmission network as part of the National Broadband Network (NBN). In many locations, this idea has been superseded by the Fibre to the Node (FTTN) system. In FTTN, most of the copper cabling and hardware from the exchange is replaced with optical fibre but it retains the final section of the copper wire CAN from pillar to customers (DA - distribution area). For example, In the subscriber distribution plan below, the cable terminal pillars and distribution cables are retained but the main cable from the exchange is replaced with optical fibre and an NBN cabinet adjacent to each pillar. The cabinet, containing optical/electrical interfaces, plus the pillar and final customer distribution cables comprise a "node". Go here for more information of NBN FTTN.
The CAN is an acronym that regularly pops up. This is/was the copper wire network between customers and their local exchange. It comprises/ed a network of pair cables and cross-connect units called MDFs (main distribution frames), cabinets and pillars. The MDF is the equipment in buildings that terminates cables and allows cross-connections. MDFs are located at both the telephone exchanges and in larger customer premises. More information on the technical aspects of telephone cables etc. can be found here.
The CAN is of particular interest today. The original intention was to wholly replace it with an optical fibre/digital transmission network as part of the National Broadband Network (NBN). In many locations, this idea has been superseded by the Fibre to the Node (FTTN) system. In FTTN, most of the copper cabling and hardware from the exchange is replaced with optical fibre but it retains the final section of the copper wire CAN from pillar to customers (DA - distribution area). For example, In the subscriber distribution plan below, the cable terminal pillars and distribution cables are retained but the main cable from the exchange is replaced with optical fibre and an NBN cabinet adjacent to each pillar. The cabinet, containing optical/electrical interfaces, plus the pillar and final customer distribution cables comprise a "node". Go here for more information of NBN FTTN.
Telephone technologies in 20th Century Australia
From Federation in 1901 through to the turn of this century, there were four main public telephone/switching technologies in the Australian network and they often existed concurrently. These technologies were:
Digital telephone systems, in particular PABXs, first appeared in the last quarter of the 20th century, closely followed by public telephone exchanges employing digital switching technology. The turn of the 21st century saw a new telephone and switching technology, digital telephony over the internet (VOIP).
Technical information on operation and repair of early telephones here.
From Federation in 1901 through to the turn of this century, there were four main public telephone/switching technologies in the Australian network and they often existed concurrently. These technologies were:
- Local battery/magneto telephony and related manual exchanges
- Central battery (CB) telephony on manual exchanges
- The automatic Public Switched Telephone Network (PSTN)
- Mobile telephony (Initially analogue but later superseded by digital technology).
Digital telephone systems, in particular PABXs, first appeared in the last quarter of the 20th century, closely followed by public telephone exchanges employing digital switching technology. The turn of the 21st century saw a new telephone and switching technology, digital telephony over the internet (VOIP).
Technical information on operation and repair of early telephones here.
The following topics are discussed below
By 2021 most of these technologies will be a distant memory, the two significant telephone technologies will be mobile (cell-phone) and NBN/internet VOIP telephony.
- Local battery/magneto/party lines
- Single wire lines
- Party lines
- Battery ringing telephones
- Central battery
- Analogue and digital telephony
- Mobile telephony
- NBN.
By 2021 most of these technologies will be a distant memory, the two significant telephone technologies will be mobile (cell-phone) and NBN/internet VOIP telephony.
Local battery/magneto systems: These were specific to point-to-point telephone connections and the earliest manual exchanges. Each phone had a local battery, typically 3V, that powered the transmitter circuit and this battery was either mounted in a separate box, or in the bottom half of the case in the old wooden wall-phones. Outgoing signalling to the exchange was typically via a hand wound, alternating current (AC) magneto generator attached to the phone. Incoming calls were signalled by a bell compatible with the magneto generator.
At the end of the 19th c. a special version of LB/magneto telephone called the "Phonopore" or "condenser" telephone was developed which enabled telephone speech to share a line simultaneously with a Morse telegraph system. In simplistic terms, it "filtered" out the disturbing Morse code pulses from the receiver. This equipment enabled economic expansion of telephony into regional areas. Some information here.
At the end of the 19th c. a special version of LB/magneto telephone called the "Phonopore" or "condenser" telephone was developed which enabled telephone speech to share a line simultaneously with a Morse telegraph system. In simplistic terms, it "filtered" out the disturbing Morse code pulses from the receiver. This equipment enabled economic expansion of telephony into regional areas. Some information here.
The image below shows an example of a mid 20th C., wooden, wall, magneto telephone. The local battery (2 x 1.5V "no. 6" dry cells) are in the bottom half, the magneto generator and handle appear upper right and the rear of the bell can be seen upper door. The handset is not visible but suspended from the switch-hook on the left side.
Single wire earth return line: The original telegraph lines were single wire/earth return. The line consisted of one wire (galvanised iron or copper) installed on insulators on poles. Stakes into the ground at both ends made contact with the earth which acted as the "second wire" or return path for the signal. This system worked well for telegraphy but put a lot of electrical noise into telephones. In WA, all telephones were LB/magneto and most operated over single wire lines until 1911. All modern telephone lines are two wire working.
Concept of single wire line (SWL). This is a telegraph line but these were also used for magneto telephony - simply substituted the telegraph key/sounder with the telephone and local battery. Original image source: Atkinson, Philip Electricity for Everybody; Its Nature and Uses Explained: (The Century Company, 1899)
Party lines: The ubiquitous magneto "Party line", still remembered by some older country residents, was where several customers were connected back to the exchange over the same line. Signalling to individuals was via a system of coded rings (I believe based on Morse code). Privacy was non-existent! I remember working on a magneto party line near Carnarvon W.A. as (relatively) recently as 1985. The last Western Australian public manual exchange closed in Tenindewa (a small wheatbelt town approx. 100 km east of Geraldton) 13 April 1985 and the last manual exchange in Australia closed at Wanaaring, NSW December 1991.
A major advantage of the above local battery/magneto phones is that they worked reasonably well over these relatively poor quality earth return lines and examples persisted in some places in Australia into the second half of the 20th century. A great story about how robust and effective these primitive lines were, can be read at:
http://www.honeysucklecreek.net/other_stations/carnarvon/Hamelin_Pool_GT1.html
http://www.honeysucklecreek.net/other_stations/carnarvon/Hamelin_Pool_GT1.html
Battery ringing telephones: Perusing early catalogues I've often noticed "battery ringing telephones". These work in a similar fashion to the above local battery/magneto telephones except that they were fitted with a direct current (DC) "trembler" bell and push button. The local battery powered both the transmitted speech signals and called the far-end bell when the button was pressed. This type of phone was generally used in private "intercom" applications rather than the public telephone network.
Central/common battery (CB) systems: The central (or common?) battery system was introduced into manual telephone exchanges in the late 19th century. Rather than local batteries at the customer end, the telephone exchange supplied the energy to the phones from a rechargeable battery bank at the exchange. Vintage CB phones are easily recognised as they have no dial, generator or local battery connection. The customer simply lifted the handset which in turn operated an indicator at the exchange upon which the telephonist answered and dealt with the call.
Although originally used in the later manual exchange networks, the CB technology easily transferred into the PSTN and the principle was still used (2017) by automatic telephone exchanges. Because it is independent of mains power, the CB system is the reason the traditional corded PSTN phone still worked during a power failure.
Although originally used in the later manual exchange networks, the CB technology easily transferred into the PSTN and the principle was still used (2017) by automatic telephone exchanges. Because it is independent of mains power, the CB system is the reason the traditional corded PSTN phone still worked during a power failure.
Analogue and digital telephony: The first automatic exchanges were electro-mechanical, analogue systems but over the course of the 20th century they evolved into sophisticated electronic, digital systems. These topics are discussed elsewhere on this page.
Mobile telephony
The ubiquitous mobile (cell) phone is now probably the biggest single personal inter-communications device in Australia (if not the world). There is a page dedicated to mobile telephony here.
The ubiquitous mobile (cell) phone is now probably the biggest single personal inter-communications device in Australia (if not the world). There is a page dedicated to mobile telephony here.
NBN: In the mid 1980s, Telecom Australia proposed to implement a nationwide digital broadband telecommunications network by the start of the 21st C. Unfortunately this plan went awry and it is over two decades late. Operating largely over optical fibres, the National Broadband Network is an integrated, high speed, data communications network that will connect all Australian premises to the internet. Eventually (2021?) our copper wire PSTN will be absorbed into the NBN and disappear. The former PSTN telephone will become a peripheral off the NBN modem and be switched via the internet. Go to this page for further information on the NBN