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Historical telephone sets

This section of the website is about historical telephones that are mentioned or featured else­where on this website. These pages are by no means intended to give a complete overview of historical telephone sets, but act merely as a placeholder for background information on them. For telephones with cryptographic features, please check our page about crypto-telephones.

Telephone sets featured on this website
Telephone sets with cryptographic features
Ericsson Model 1951
Heemaf Model 1955
US military Autovon switched telephone network
GPO series 300 telephones
GPO series 700 telephones
Dutch PTT standard telephone set with pulse dialling
Dutch PTT standard T65-TDK with DTMF dialling
Krypto-Fernsprecher 4-2
Defense Red Switch Network
Cisco 7962G Unified IP Phone
CIS Secure DTD-7962-T2 TEMPEST version of Cisco 7962G Unified IP Phone
GSMK CryptoPhone IP-19
Mobile phones
Dutch variant of the AEG 4015C, for use on the Dutch ATF-1 network
Dutch variant of the Motorola Pulsar II VHF, for use on the Dutch ATF-1 network
Hacked German Becker car phone (Telefunken)
CARVOX 2451 - used for phone phreaking
Nokia Mobira RD-59 (CARVOX 2453)
Nokia RD-72 used as emergency backup phone
Related subjects
Frequency Changer No. 6AC/3 - British wartime telephone scrambler as used by Churchill
Wire tapping and wirless tapping
Home-made ATF-1 carphone phreaking unit
Pocket organiser with built-in fax machine (1994)
Subscriber Identity Module
Related subjects
Mobile public networks
Dialling standards
  • Pulse
    Pulse signalling is the oldest standard for dialling a number over a subscriber line on an automatically switched exchange. The telephones have a rotary dial that – when operated – interrupts the line current at 10 pulses per second. For this reason it is also known as a loop disconnect system [1]. In the 1970s and 80's, when button-operated telephone sets became mainstream, many of them simulated the loop disconnect pulses.

  • Tone
    In 1963, the Bell System (USA) introduced push-button dialling by means of Dual-Tone Multi-Frequency signalling (DTMF) under the name Touch-Tone [2]. It allowed faster dialling and was less prone to mistakes. In Europe it was known as DTMF or MF4, but was not introduced until the 1970s and 80s. And even then, many push-button phones still simulated pulse-dialling as the exchanges had not yet been converted to DTMF.  More

  • ISDN
    ISDN was a set of digital communications standards that could be implemented over existing PSTN (copper) wiring. The signalling was sent over the network as part of one of the digital protocols. ISDN was short-lived and was succeeded by ADSL and VoIP.  More

  • VoIP
    With the arrival of wideband internet, many telecom operators have converted their networks to IP-based communications, using the Voice-over-Internet Protocol (VoIP). With this protocol, signalling information is typically sent as out-of-band data, using the Session Initiation Protocol (SIP).
Wiring standards
Old analogue telephone lines (POTS) commonly only need two wires for the connection between a telehone set and the telephone line. Power, signalling and audio is passed over these two wires. Although there are many different designators for these wires, the most common European name for them is (A) and (B). In the US, they were known as Ring (R) or (-) and Tip (T) or (+). Further­more, each country used to assign its own colour scheme to the wiring. To avoid confusion, we will use the European designators (A) and (B) here, and colour them red and blue respectively.

Modular jack
Modular jacks — also known as Registered Jack (RJ) connectors — are a relative simple yet reliable way to connect (analogue) telephone equipment to a telephone line. The connector was initially developed in the United States, but has since been adopted worldwide. They exist in many forms:

Although there are many variations, the most popular ones are shown above. The specified pin-numbering is when looking into the female socket, (i.e. not the plug). At the centre are the contacts that are used for connection to old analogue telephone lines (POTS), with the official modular designator at the bottom. It shows the number of positions (P) and the number of actual contacts (C). To avoid confusion, the official designator should be used instead of RJ-something. At the right is the RJ45 or 8P8C ethernet connector, which is shown here for comparison only.

 More about Registered Jack (RJ) connectors

American standards
In the US, 6P2C, 6P4C and 6P6C connectors were used for single-line, two-line and three-line configurations respectively, as shown in the diagram below. The most common wiring is for a single-line, which is always connected to the middle two contacts, regardless the connector type. The single-line US standard was adopted by most countries in the world, with some exceptions.

European standards
In Europe, the situation was much more complicated, as each country traditionally had its own type of connector and wall socket. The introduction of the Registered Jack did not take place until the mid-1970s, when foreign equipment was gradually being allowed on European networks.

Although most countries have meanwhile adopted the American standard – shown on the left – the UK uses the outermost two contacts of a 6P4C connector, whilst Belgium uses the rightmost two contacts. This leads to compatibility issues when connecting foreign equipment to a line. To avoid confusion, Crypto Museum suggests to wire the wall socket as per rightmost diagram.

Crypto Museum standards
With analogue lines (POTS) gradually disappearing and ethernet cabling becoming much more common, we have been looking for a simple way to distribute old analogue lines throughout the premises, using modern cabling standards, such as Cat-3, Cat-5, UTP and STP, and RJ45 jacks.

Above is the wiring scheme we use at Crypto Museum for the connection of up to four analogue telephone lines via regular ethernet wiring, taking the common twisted-pair wiring order into account. We have created small breakout boxes to provide upto 4 analogue lines, some of which we have modified by shorting lines 3-5 and 4-6, so that one of the sockets accepts any type of 2-wire equipment, regardless the connection variant (American, European, British or Belgian).

Below is the wiring for a standard handset as it is used on most modern POTS telephone sets. It uses the smaller RJ9 (4P4C) connector that is in most cases wired with a coiled cable.

Older standards
Below is the pinout of a Dutch analogue subscriber line, as endorsed by the (then) state-owned provider PTT. This is the pinout when looking into the wall socket, which is the same as looking at the screw terminals inside the instrument's plug (shown here). When no external bell is connected, a wire strap should be placed in the wall socket, between the B and EB contacts.

  • a
    Subscriber line (A) red
  • b
    Subscriber line (B) blue
  • EB
    External bell (normally strapped to b) 1
  • GND
  1. The (EB) terminal is normally strapped to (b) terminal inside the wall socket. It is removed when an external bell set is connected to these terminals. If the phone doesn't ring, check whether this strap is present.

  1. Wikipedia, Pulse dialling
    Retrieved July 2021.

  2. Wikipedia, Dial-tone multi-frequency signalling
    Retrieved July 2021.
Further information
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Crypto Museum. Created: Thursday 30 March 2017. Last changed: Monday, 15 April 2024 - 08:54 CET.
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