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Interfacing Teletypes and Paper Tape

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    Volumes

    1. Vol 1 Interfacing Teletypes and Paper Tape — Vol 1: The Current Loop Why a teleprinter signals with current instead of voltage, neutral and polar loops, 60 mA and 20 mA, what the selector magnet's inductance does to every edge, the arithmetic of a loop, how to measure one, and how not to be hurt by it.
    2. Vol 2 Interfacing Teletypes and Paper Tape — Vol 2: Loop Supplies, Old and New The station rectifiers and Navy supplies the machines were built for, the hobbyist's transformer-and-resistor supply, spark suppression on the contacts, and a complete modern design: 48 volts, a MOSFET current sink and a clamp, worked through value by value.
    3. Vol 3 Interfacing Teletypes and Paper Tape — Vol 3: Talking to a Computer — the Hardware Sensing a loop with an optocoupler, keying one with a high-voltage transistor or MOSFET, keeping the computer isolated, which USB-serial chips can and cannot do five bits at 45 baud, the ASCII machines' passive loops, and the interfaces that exist today.
    4. Vol 4 Interfacing Teletypes and Paper Tape — Vol 4: Talking to a Computer — the Software The start-stop character and its odd speeds, ITA2 and US-TTY, the LTRS/FIGS dance and unshift-on-space, getting 45.45 baud out of Linux, a USB chip or a Pico's PIO, the programs that drive teletypes today, and how the ASCII machines differ.
    5. Vol 5 Interfacing Teletypes and Paper Tape — Vol 5: A Real Machine on the Air RTTY.COM and its archive, terminal units old and new, putting a teleprinter between an HF rig's audio and its keying line, and a worked example: printing the ITTY news on a real teletype.
    6. Vol 6 Interfacing Teletypes and Paper Tape — Vol 6: Paper Tape In and Out of the Computer The tape as a data format, chadded and chadless, punching tape from a computer, reading it back through a transmitter-distributor or an optical reader, eyeball banners and Baudot art, and archiving old tapes by scanning them.
    7. Vol 7 Interfacing Teletypes and Paper Tape — Vol 7: Two Builds — a Pico Loop Interface and an Optical Tape Reader A Raspberry Pi Pico interface that puts any 60 mA or 20 mA teleprinter on USB, with its schematic, parts, firmware and bring-up; a hand-pulled optical reader for 5- and 8-level tape; and the PURPLE cipher-machine replica they are meant for.