Click for homepage
Phones
PTT
  
T65 →
  
T65-TDK
Analogue desktop DTMF telephone set

T65-TDK was the standard analogue telephone set with DTMF touch-tone dialling, for the Public Switched Telephone Network (PSTN) in the Netherlands, introduced in 1974 by the Dutch telecom monopolist PTT (now: KPN). It is the DTMF version of the standard T65 dial-operated telephone.

The shape is based on the 1965 design of the standard Dutch dial-operated T65 telephone set from the German manufacturer Krone, hence the name T65-TDK. The suffic 'TDK' means Toon-Druktoets-Keuze (touch-tone dialling). It used Dual-Tone Multi-Frequency (DTMF) signalling.

The T65-TDK was only suitable for subscribers who were connected to a computer-operated switch that was capable of handling DTMF tones, which excluded part of the country at the time. Furthermore, PTT charged a one-off fee to each subscriber for enabling the use of DTMF tones.
  
T65-TDK made in 1979 by Ericsson

The T65-TDK was first manufactured in 1974 by Ericsson, followed in 1977 by NSEM and in 1979 by Krone. The DTMF units of Ericsson and Krone are interchangeable, but the one from NSEM is not, as its keys are positioned differently. As a result, the grey upper case shell is also different. The sets were available in grey, green, orange, red and brown – with different colour accents – and were in production until the mid 1980s, when they were succeeded by new slimline designs.

Apart from the numbers 0 to 9, the DTMF keypad has two additional characters – ✱ and # – which gave access to a range of (switch-dependent) options, such as wakeup call, answering service, follow me, etc. In the Netherlands, most of the extra features were initially disabled by PTT, and only very few features were eventually released to the public over time (for additional fees).

T65-TDK made in 1979 by Ericsson
Front view
Bottom
Connections and model tag
T65-TDK manufactured by NSEM in 1978
T65-TDK with optional extra speaker
Front view
Extra speaker connected at the rear of the set
A
×
A
1 / 8
T65-TDK made in 1979 by Ericsson
A
2 / 8
Front view
A
3 / 8
Bottom
A
4 / 8
Connections and model tag
A
5 / 8
T65-TDK manufactured by NSEM in 1978
A
6 / 8
T65-TDK with optional extra speaker
A
7 / 8
Front view
A
8 / 8
Extra speaker connected at the rear of the set

Options
  • Earth button
    Initially, the T65 was available with and without an Earth-button, that connected the A-wire of the telehone line briefly to ground, to pass a call to the (optional) PABX. From 1973 onwards, the earth-button was present on all T65 units.

  • Colour
    The initial colour was (green-ish) grey with a cream bottom, dial and other details. In the 1970s, the phone also became available in a variety of colours, including red, green, white, brown, blue and orange, some of which are very rare today.

  • Lock
    A lock could be added – in the front left corner – to block outgoing calls. It shorted the contacts of the dial, and incoming calls could be answered as usual. Despite the lock, outgoing calls were still possible by tapping the hook switch in the correct rythm.

  • Volume control
    Handsets were available with an integrated knurled knob, that could be used to adjust the volume of the additional built-in amplifier.

  • Microphone amplifier
    An additional microphone amplifier could be added for people with a soft voice. It had to be enabled with a small black slide switch at the rear of the handset. This option is rare.

  • Mute button
    Handsets were available with a push-button that disconnected the microphone as long as the button was depressed. It was located at the same place as the volume control (above). The green variant of this option was also used on the NATO KF 4-2 voice terminal.

  • Noise-cancelling microphone
    For use in noisy environments, such as aboard ships and in military bunkers, a special noice-cancelling microphone was available. It was fitted instead of the regular micro­phone and was slightly thicker.
DTMF conversion kit
For the conversion of standard T65 telephone sets to touch-tone dialling, circular DTMF units were made by Ericsson. These were particularly useful for the W65 and I65 models, which were not available in a DTMF variant as standard.

It has the same form factor as the old interruptor (pulse) dial, so that it could be retrofitted to any existing T65, regardless the manafucturer.
  
Circular DTMF until for replacing the old pulse dial


Interior
Bottom
Connections and model tag
Disassembled NSEM T65-TDK
Interior
NSEM DTMF panel
NSEM T65-TDK interior
Basic telephone set
B
×
B
1 / 7
Bottom
B
2 / 7
Connections and model tag
B
3 / 7
Disassembled NSEM T65-TDK
B
4 / 7
Interior
B
5 / 7
NSEM DTMF panel
B
6 / 7
NSEM T65-TDK interior
B
7 / 7
Basic telephone set

Connections
Line
  • Red
    a
    Line (A)
  • Blue
    b
    Line (B)
  • Green
    E
    Earth (ground)
  • Yellow
    EB
    Extra bell (strapped to b in wall socket)
Handset
  • Red
    T
    Speaker (1)
  • Blue
    T
    Speaker (2)
  • Yellow
    M
    Microphone (1)
  • Green
    M
    Micriphone (2)
Subscriber line
  • a
    Subscriber line (A) red
  • b
    Subscriber line (B) blue
  • EB
    External bell (normally strapped to b) 1
  • GND
    Ground
  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.

Known manufacturers
  • Ericsson
  • Krone
  • NSEM - Nederlandse Standard Electric Maatchappij BV
Further information
Any links shown in red are currently unavailable. If you like the information on this website, why not make a donation?
Crypto Museum. Created: Thursday 30 March 2017. Last changed: Friday, 06 August 2021 - 07:13 CET.
Click for homepage