5-BIT TELETYPES

MODELS 14, 15 AND 19

Teletype Model 19 Restoration Series Playlist:

Introduction to Baudot Teletypes and Documentation Archive

The 5-bit Teletypes restored here were introduced in 1925 (Model 14), 1930 (Model 15) and 1940 (Model 19), and are all very closely related, sharing similar mechanisms. They do not use the modern 8-bit ASCII code, but instead they use the 5-bit Baudot code that preceded it. As such, they make very poor machines to connect to computers. However they are incredibly robust text transmission systems. These units are military grade, and were workhorses in the Army and Navy through the second world war and the Vietnam war. They found extended civilian use in the Telex system, and were used in newsrooms until the mid 1980's.

I have uploaded a large set of documentation that we have used throughout the restoration:

The essential individual documents in this set are linked below in context.

Episode 1-3: Main Documents

Teletype Model 19 Restoration

This videos is a demo of our fully restored Model 19 and Model 15 5-bit Baudot Teletypes. Although this was shot at the very end of the restoration series, it provides the best introduction to the machines by explaining the principles and showing them in use.

Here are the main reference documents to the Model 15/19 Teletypes:

Navy Guide to Teletypes

This manual is the best introduction to 5-bit Teletypes I have found. It gives a great introduction to the basic principles and describes various machines and use cases.

Model 15 Printer

This is the main manual for the printer (receiver) section of the Teletype (both for the Model 15 and Model 19)

Model 19 Table

The devilish wiring of the Model 19 table got us stumped for at first. The above collection of schematics helped us disentangle it.

Model 15 Keyboard and Punch

This is the manual for the keyboard and punch section.

Model 19 Base

This manual has the complex wiring for the base that holds the keyboard, printer, motor, polar relay and external interconnect block.


Episode 2 Documentation: TTYLoopDriver and BaudotRSS

5-Bit TTY Interfaces

In this demo we use a modern 60 mA interface to print newsfeeds on our teletype

John Nagel TTYLoopDriver

A 60 mA Baudot USB adapter for working with the BaudotRSS software below. Derives its own high voltage supply from the USB power, which is very neat. It is good hardware, but the description and documentation of the project is poor. It says it does not need drivers, but it sure does, and they are hard to find. Carl managed to build one.

John Nagel BaudotRSS

Software to use with the above hardware interface. Can be used to print rss news feeds. Similar to the above, nicely done, but difficult to get going. We eventually managed to make it work when we discovered it only works with Python v2.7. It requires a whole bunch of extra packages. COM ports numbers are off by one (use 0 to talk to COM1!). It eventually worked.

Episode 4 Documentation: Power Supply

REC-30 Teletype Power Supply

This high voltage DC power supply uses blue-glowing thyratron tubes.

Ken Shirriff's in-depth article about the power supply:

http://www.righto.com/2018/09/glowing-mercury-thyratrons-inside-1940s.html

Power supply schematics:

Episode 5-6 Documentation: Model 15 Keyboard and Punch

Keyboard and Punch

It takes two episodes to repair the keyboard and the tape punch unit. The punch counter gives us particular trouble.

Episode 9 Documentation: Model 15

Fixing the Model 15

Getting our Model 15 to work necessitates a deep dive into the actual wiring and adjustments of our particular unit. We unearth a few subtle faults introduced during a previous restoration attempts.

Episode 11: Visiting Mr RTTY

Paul Cembera has probably the last remaining collection of spare parts for Teletypes

Tel: (510) 222 3102

mr_rtty@pacbell.net

http://www.johnwhitney.com/misc/paul-rtty.htm

RTTY Electronics

PO Box 20101, El Sobrante, CA 94820-0101 USA

Episode 12 Documentation: Model 14 T/D

Model 14 T/D (Transmitter Distributor)

This units reads previously recorded punched tapes for transmission.

Episode 13 Documentation: Model 19 Table

Model 19 Table Wiring

The complete rewiring of our Model 19 table forces us to finally reverse engineer the apparently incomprehensible wiring arrangements.

Episode 14 Documentation: Adding the Motor Stop Feature

Adding the motor stop feature

Quite a number of features are optional on the series 15. In this episode, we add the motor stop feature.

We found all the parts at Mr. RTTY, referenced above.

Episode 15 Documentation: Model 14 Reperforator

Model 14 Reperforator

We add one final piece of 5-bit teletype equipment: a reperforator.