retrointerfacing

Commissioned by Trotec Laser as present for Trodat’s 100 year anniversary: a retro clock shaped like one of Trodat’s modern stamps… The used acrylic was all laser cut of course

The Recycled-Robots roadshow presented at the Twente Biennale 2011!

See the youtube clip below:

Using a telephone retro-interface and Arduino wav-shield-derivative a box has been build which allows you to use an old rotary phone as standalone dial-a-song system. This makes an excellent CD-pre-listening device for our CD-sales stand at concerts.

The system is fully documented (including schematics, software, PCB layout) on the wiki. Although numerous designs have been made where the innards of rotary telephones have been replaced by other electronics (birthday card sound chip, GSM telephone), this project has a completely different approach. No changes to the telephone have been made. The phonebox generates line-voltage, even the 90V 20Hz ringer voltage. A sound input/output is added for line level signals. The box is powered using 12V dc, so mobile operation is possible.

The idea (accidentally re-invented) is not new - so it is in two respects a retro-interface From wikipedia: Established by rock band They Might Be Giants (TMBG), Dial-A-Song consisted of an answering machine with a tape of the band playing various songs. The machine played one track at a time, ranging from demos and uncompleted work to fake advertisements the band had created.

So basically this design is your dial-a-song-in-a-box….

Although most modern telephones have GPS installed - this project takes things a little differently. An old rotary phone is connected using the phonebox to a GPS antenna. Stories are being recorded and stored with location data in the device. When the device re-visits the location, it will give a phone call using the earlier stored message. See the phone in action on the ‘kunstfietstaxi’ in the following clip:

The electronic system has been used in a stand-alone ‘voicemail-box’ and in this GPS-enabled taxi phone. The voicemail box (’phonebox’) is on display at the ‘MultiSolo’ exhibit. More links on the taxi are the following: ‘kunstfietstaxi’. - see also youtube or this clip and TVenschede.

Yezz! another retrointerface ready. The phonebox simulates all necessary signals to operate a rotary-dial style telephone to any other device. Dialed numbers are put through to a serial port. For audio connection a line-in and line-out are given. The board puts a 12V line-voltage on the phone, and can also generate the 70V - 20Hz voltage for the ringer. Technical details will be put on the wiki. The schematic is inspired by the linesim design, but uses a microcontroller (atmega168) and has amplifiers for audio in- and output. It works with standard (dutch) rotary dial phones (Ericsson T65 and older)

It has been used in a stand-alone ‘voicemail-box’ and GPS-enabled taxi phone. The voicemail box (’phonebox’) is on display at the ‘MultiSolo’ exhibit. A GPS enabled version has been installed in a taxi-bike called ‘kunstfietstaxi’. - see also youtube and TVenschede.

The first RetroInterface is a fact!. I used an Ottantotto to convert the signals to and from a T100S telex by Siemens to ‘modern day ASCII’ at 9600 baud. The system works well. Any type of terminal emulator on PC can be used to write and read data (half duplex) to the telex.

Apparently the Telex was already prepared in earlier times to get the line current from an internal source. I had to make a little circuit using a couple of resistors and an optocoupler to get the data out (50 baud). I used a modified version of the SoftSerial library that comes with Arduino. Apparently it uses the ‘delayMicrosecond()’ function which does not perform well in delays over a couple of milliseconds. (So the softSerial lib is not so good for datarates < 1200 bd I guess) For transmitting data two relais have been used, one to switch the internal current trough the data relais (necessary to disconnect the receiver side, otherwise you'd always echo all data) and the other to transmit the data. Especially getting the timing for the transmit pulses right was quite some work. The switch on period needed to be slightly shorter than the switch off. (shorter 1's than 0's). Also the startbit needed to be longer than the expected 20 msec. Source code and schematics will be posted on the wiki.

I made use of various great sources on the web for retrieving data on these machine. Johan (rtty.nl) has been of great help by scanning some old books on telex for RTTY! Also the sites teleprinter.net and rtty.com have an abundant amount of information.

The telex will be used in an installation ‘de taalmachine’ (language-machine) by de Spullenmannen in Amersfoort.