PX1000 was a small hand-held message terminal, that was used for creating
and sending text messages over standard telephone lines, using a built-in
acoustic coupler. The PX-1000 was introduced in 1985 by
in Amsterdam and was sold by Philips
(Netherlands) and others.
Although different versions of the PX-1000 were sold,
we will concentrate here on the Philips version of the PX-1000Cr,
as it features advanced cryptographic capabilities.
It was intended for small companies and journalists, and was also used by
the Dutch Government.
Furthermore it played an important role in the fight for
Nelson Mandela's release from prison.
The image on the right shows the Philips version of the PX-1000Cr.
The extension 'Cr' is used to identify the crypto-version.
It is shown here with its display up (i.e. the highed top lid open).
The intial PX-1000 was introduced by
Text Lite in 1980. It was
capable of sending sending messages up to 7400 characters via
a standard analogue telephone set, using the built-in acoustic
modem. As a countermeasure against eavesdroppers, the text could
be encrypted with the DES encryption algorithm. In 1983,
the NSA expressed its concern about the
availability of the DES algorithm to the general public
and ordered Philips Usfa
to develop an alternative algorithm.
During the development of the alternative encryption algorithm
by Philips, an intermediate version of the PX-1000 was sold.
In this version the encryption facilities had been replaced by
a simple spreadsheet. It became known as the CALC-version as
it had a blue CALC-button replacing the standard red CODE-button.
Once the new algorithm was ready, in 1984, the red CODE-button was
re-introduced and the unit became known as the PX-1000Cr
(Cr = Crypto).
Both versions were adopted by Philips
and sold in the Netherlands as PX-1000 and PX-1000Cr.
in 1985, a version with C-Mail capability (but without crypto)
was added to the range. Several other variants,
such as the Family Doctor,
appeared in other countries under various names like Siemens, Alcatel and Commex.
The PX-1000 was followed by the slightly improved PX-1200 and finally
by the completely redesigned PX-2000.
Text Lite BV is not longer in business.
Short messages were stored in the PX-1000's static memory, that was
retained by the internal batteries (7400 characters max.).
Longer messages could be stored on an external audio cassette recorder,
by connecting a short 3 mm Jack cable to the
microphone input of the recorder. They could be loaded back into the
PX-1000, by connecting the same cable to the headphones output of the
recorder and playing back the message.
The PX-1000 was fully designed and developed by
Text Lite BV in
Amsterdam (Netherlands) in 1979 and 1980.
The case was designed by company shareholder Hugo Krop, who was also
repsonsible for the functional specification of the device.
The actual PX-1000 units were manufactured by Samwell
Electronics in Taiwan, whilst Text Lite Ltd. in Ireland was
responsible for the the final quality assurance and packaging.
The first units appeared on the market in 1980.
From the outset, the PX-1000 was capable of sending messages
in encrypted form using the DES encryption algorithm, which had
been obtained from the American Bureau of Standards for just US$ 8 .
By 1983 however, the National Security Agency (NSA)
in the US became aware of the PX-1000 and its encryption capabilities
and god increasingly concerned with the DES algorithm being available
to the general public world-wide in such a small and affordable device.
In The Netherlands,
had the exclusive distribution rights of the PX-1000 and was
probably the largest customer of
Text Lite BV.
After the NSA had expressed its concern
about the use of DES, Philips Usfa
was asked to develop an alternative encryption algorithm.
At the time, Philips Usfa
was heavily involved in confidential
work for the Dutch Government and for NATO and had a
that had specialized in cryptographic equipment.
As they had already implemented an
NSA encryption algorithm
in their Spendex 40 secure phone,
they had built a good relationship with the
It was decided that Philips Usfa would develop a new algorithm
for the PX-1000, which was done at Philips Usfa in Eindhoven
(Netherlands) under close observation of Text Lite
engineers who were concerned of any hidden 'backdoors' .
As no backdoors were found, the algorithm was approved for the
new PX-1000Cr. It was also decided that Philips would buy
the remaining stock of 'old' PX-1000 units and all ROM-sets that
had already been manufactured.
In 1985, Philips sold the 12,000 old PX-1000 units and
20,000 masked ROMs to the Americans, for a total value of
NLG 16.5 million (7.5 million Euros) .
Please note that unlike other Philips encryption devices,
the PX-1000Cr was not a product of
Philips Crypto BV.
Instead it was marketed and sold by the ELA Group of
as a consumer product.
According to the instruction manual of the PX-1000Cr ,
the number of possible cryptographic keys was calculated at a mere
18,446,744,000,000,000,000 (over 18 quintillion).
It would take the fastest computer
thousands of years to break it... [7 p.16].
The PX-1000Cr was also used by parts of the Dutch Government during the 1980s.
For official government use however, the Philips software was replaced by
their own in-house developed version, containing a secret encryption algorithm.
No details about this algorithm are available.
Several different versions of the PX-1000 are known to exist. They were
sold under a variety of brand names, but this was not a simple matter of
rebadging the product, as there are some signifficant differences between the
various versions. Globally speaking, there were three different versions.
Most items shown on this page are courtesy Cees Jansen .
- Text Tell PX-1000
The standard version was a simple text terminal,
that allowed messages to be entered, stored and transmitted over a standard telephone line. It had built-in DES-based encryption/decyption.
It can be recognized by the red MODE-button.
This version was developed in 1980 and is different
from the Philips PX-1000Cr (see below).
Firmware: COPYRIGHT TEXT LITE 1983 (ROM).
- Text Tell PX-1000 CALC E
In this version, the text encryption/decryption feature has been dropped
in favour of an arithmetic calculator.
It can be recognized by the blue MODE-button.
The packing was modified by sticking an adhesive label over part of the text,
but the image of the PX-1000 with the red button, remained on the packaging.
- Family Doctor (C-mail)
This version of the PX1000 was sold in the USA as an aid to send and read
ECGs (Electro-Cardiograms). The terminal had a
rebatched display panel
with the words 'Family Doctor' at the top.
It supported the C-Mail message protocol
(E-mail via the command-line).
Photograph below courtesy Detlev Vreisleben.
- Philips PX-1000
This was basically the standard Text Tell PX-1000 with the built-in
arithmetic calculator. The only difference is the
Philips logo on the
product and on its packaging.
Firmware: COPYRIGHT 1984 WEST-TEC PX CALC E (EPROM)
- Philips PX-1000Cr
This was the Philips implementation of the
cryptographic version of
the PX-1000. The arithmetic calculator was dropped in favour of the
improved encryption/decryption algorithm. This version was not compatible
with the earlier Text Tell PX-1000.
Firmware: COPYRIGHT 1984 WEST-TEC PX V2 (EPROM)
- Philips PX-1000 C-mail version
This was an adapted version of the standard PX-1000 that allowed messages
to be sent via C-mail, an early protocol to read SMTP E-mail from the
This version has no cryptographic capabilities.
Firmware: COPYRIGHT 1985 WEST-TEC PX CALC H (EPROM)
- Government version of the Philips PX-1000Cr
For use by the Dutch government, a special version of the Philips PX-1000Cr
was used. It contained an improved (secret) encryption/decryption algorithm.
The cryptographic software was not developed by Philips, but by a specialized
Each PX-1000 terminal has a built-in
RS-232 serial port which is combined with
the power connector at the left. The RS-232 connection allows the matching
PXP-40 printer to be connected at the left hand side.
Power is then connected to the rear of the printer.
The PXP-40 is a small 40 column thermal printer, roughly about
3/4 of the width of the PX-1000. It is
inserted into a slot at the left side
of the terminal and can be released again
by pressing the two release buttons.
When unused, it is stored in its
The image on the right shows a Philips-branded PXP-40 printer,
loaded with a paper roll. Paper can be transported manually by rotating
a rigged knob at the left.
Paper is loaded from the rear and the roll
simply rests inside its bay,
with no axle to hold it in place.
Further images of the PXP-40 in use, below in the thumbnails.
Click any of them to enlarge. The last two images show how the two
release buttons (one at the front and one at the rear) have to be
pressed simultaneously in order to
remove the printer from the PX-1000 again.
It was also possible to use the PX-1000 with a different type of
printer. By using a 3 mm Jack-to-DB25 cable,
any suitable printer with a serial port could be used.
- Data rate: 300, 600 or 1200 baud
- Data format: 7E2 (7 data bits, even parity, 2 stop bits)
- Power: 12V DC via external adapter
- Display: Single line monochrome LCD
- Memory: 7400 characters
- Modem: simplex
On 11 February 1990, black activist Nelson Mandela was released from prison,
after serving nearly 28 years of his life-time sentence.
Mandela was the leader of the South African political organization ANC
(African National Congress).
During his imprisonment, many people from all over the world fought for his
release and for the abolishment of Apartheid.
In 1986, a secret operation led by then-ANC intelligence officer
Mac Maharaj was mounted, to smuggle freedom fighters into the
country and prepare Mandela for his speculated release:
Operation Vula  (Eng: commence).
The Dutch contribution to Operation Vula was led by Connie Braam,
then head of the Dutch anti-apartheids movement.
Her work involved finding professional makeup artists for making
disguises, a stewardess acting as a courier and, last but not least,
a modified Philips PX-1000 that was used to exchange messages
with Mandela in his prison cell on Robben Island.
On 11 February 2010, the Dutch TV program Andere Tijden, aired a
25 minute special about Operation Vula . In the interview,
Connie Braam explains how she contacted an engineer who worked for
Philips at the time. He suggested the PX-1000 for secure communication,
which was subsequently used to send messages to Nelson Mandela
via Amsterdam and London.
The first trial went well, but the PX-1000 would not work reliably
over the South African phone system . They had to revert to their
earlier method of using recorded modem signals on tape recorders and
answering machines. Various encryption methods were implemented,
including One-Time Pad and variable key length.
This resulted in the need to send a floppy with the necessary codes
to South-Africa, which was done by a KLM stewardess who was recruited
as a courier by the movement.
On the day of his release from prison, Mandela, who was assumed
to have lived his years in complete isolation, surprised the world by
being fully informed and giving a strong political speech.
The PX-1000 was extremely well built for its time. It was also very compact and
light weight, which made it ideal for portable applications. It was among the
first devices to use an advanced microcontroller with integrated memory and I/O:
the Hitachi HD6303RP.
The image on the right shows the PCB inside the PX-1000. The small
circuit board is very well layed out and carries the
processor (in DP-40 packaging) right at the center.
The controller is compatible with the Motorola 6800 series,
and has a built-in serial interface (SCI), parallel I/O,
timers and 128 bytes of RAM.
Memory is further extended by using a HM6264 external static RAM (right).
This adds 8KB of RAM to the design, 7.4KB of which is available for storing
the text messages.
The software is stored in an 8KB EPROM (left of the RAM).
The modem of the PX-1000 is implemented as so-called
thick film circuit.
It consists of a number of SMD components (transistors, diodes)
and vapor deposited resistors, on a white ceramic substrate. It has two
rows of pins, one at either side, for connection to the motherboard.
In the image above, the thick film circuit is located on the left half of the PCB.
A separate audio pre-amplifier (Toshiba TA7330P),
with automatic level control (ALC), is present to the left of the thick
film circuit, in between the two potentiometers .
Inside the PX-1000 are 5 Varta 170 DK NiCd battery cells. As each NiCd cell
has a nominal voltage of 1.2V, the PX-1000 is normally powered by 6V DC.
As the PX-1000 was built somewhere around 1985, the NiCd batteries of most
of the surviving devices will have died by now. Furthermore, NiCd batteries
have the tendency to start leaking after so many years, causing permanent
damage to the interior of the PX-1000. This is clearly visible below.
If you want to bring an old PX-1000 back to life, you first need to remove
the old batteries and clean the interior. Next, you'll need to examine any
damage caused by the leaking batteries and repair that if possible.
Finally, you need to find a suitable replacement for the batteries.
One possibility is to bring the wires out, and feed the PX-1000 with an
external 6V DC power supply.
A better solution however, is to replace the 5 cells by the newer
Varta V250H NiMH cells.
These cells have been designed especially to replace the old 170DK NiCd
Replacing the cells is a clean solution that doesn't require any
modifications to the PX-1000 itself. One has to bear in mind though,
that the replaced batteries should be used (discharged) and charged
regularly, in order to keep them healthy. The is also true for the PXP-40
The image on the right shows what happens to the interior of the PXP-40
printer, once the batteries start leaking. In this case, the swollen batteries
have caused permament damage to the printer mechanism. The leaking batteries
have also caused corrosion to the main PCB.
The PXP-40 is powered by 7.2V. The 6 NiCd cells of 1.2V each, are bound
together as a pack, positioned aside the printing mechanism on top of the
PCB. They pack is connected to the main PCB by 2 wires that also keep it
in place. The batteries are easily replaced.
Bringing a PXP-40 printer back to life, might be a bit more work than getting
a PX-1000 to work. As the batteries are located aside the printing mechnism,
the cog wheels are easily damaged by the swollen batteries. Careful cleaning
and reparing of the broken parts will often be necessary to bring the PXP-40
back to life.
Leaking batteries may also cause secundary damage to the PCB. As a result
of the swollen batteries, the cog wheel mechanism can be blocked, causing
excessive currents in the motor driving electronics. This may cause a
56 ohm safety resistor on the PCB to break.
The PX-1000 was supplied with its own transit case, a mains power adapter
and a manual, stored in a rectangular carton box with a photograph of
the device on the sleeve. Inside the box was a polystyrene placeholder
with a layer of dark blue artificial velvet (see below).
The packaging could be tailored for each reseller,
but always contained the TEXT TELL logo.
There were small differences in the typeface
and in the text printed on the carton.
The image on the right shows the packaging of the Philips
PX-1000Cr. It contains the Philips brand name in the
top right corner and the TEXT TELL logo at the bottom.
Other (but similar) cartons can be found in the thumbnails below.
The Text-Tell PX-1000 under various brand names. The following names
are currently known:
- Commex, Teli Contact
- Family Doctor
- Text Tell Ltd.
7 Montpelier Parade
Monkstown Road, Blackrock
- Text Lite BV (1985)
Corn. Schuytstraat 74
1071 JL Amsterdam
Our call for documentation of the PX-1000 in mid-2011 has generated a new flow
of information about this device. The original user instructions were found
rather quickly, but we were really surprised when we received the original
service manual and the circuit diagrams. We've now made them available for
download below in the hope that they may prove useful when repairing a broken
PX-1000. Many thanks to all who have contributed.
If you use the documentation, please consider making a
donation to Crypto Museum.
- Philips Nederland BV, PX-1000 Brochure
8-Page full-colour brochure (Dutch). Probably 1985.
- Philips Nederland BV, PX-1000 Handleiding
User Manual (Dutch). 29 pages, A5 size, B/W. April 1985.
- Text Tell Ltd, PX-1000 Operating Instructions
User Manual (English). 19 pages, A5 size, B/W. 1985.
- PX-1000 and PXP-40 Service Manual
Full circuit description of version H. 61 pages, A4 size, B/W.
- PX-1000 Circuit Diagrams
Version F and H. 4 pages, A3 size, B/W. 1985.
- Cees Jansen (former cryptographer at Philips Usfa/Crypto)
Interview at Crypto Museum, August 2011.
- Noseweek, Zuma, SARS and Kebble: The Political Agenda
Issue 69. 1 July 2005.
- Andere Tijden, The Making of Nelson Mandela.
TV program by NPS, VPRO. 11 February 2010. 25'24" (Dutch).
- WayBack Machine, www.texttell.com
Internet archive, showing the state of the Text Tell website in 2001.
- Hitachi, HD6303RP microprocessor datasheet
- Toshiba, TA7330P pre-amplifier datasheet
Pre-amplifier with ALC circuit for mini/micro cassette tape recorder.
- Philips Nederland, Philips PX 1000 Handleiding
Manual for the Philips PX-1000 and PX-1000Cr (Dutch).
- Tim Jenkin, Talking to Vula
The story of the Secret Underground Communications Network of Operation Vula.
ANC website. ANC's Montly Journal Mayibuye, May 1995 - October 1995.
- US Patent D282164, Portable Telex case or the like
Filed 17 Oct 1983 on behalf of Text Lite BV. Granted 14 Jan 1986.
- Onkruit, De klanten van Philips Crypto
The customers of Philips Crypto (Dutch). June 1992.
Documents captured by activist Kees Koning after breaking into
the offices of Philips Usfa.
- Hugo Krop, Personal correspondence
Crypto Museum, 25 August 2013.
Any links shown in red are currently unavailable.
If you like this website, why not make a donation?|
© Copyright 2009-2013, Paul Reuvers & Marc Simons. Last changed: Wednesday, 11 December 2013 - 17:21 CET