Alger Salt and the VOTEM
Alger joined and took us back to the early 1980s, when he and a colleague built an analog interface for the ZX81/TS1000 cassette input. The device—named VOTEM (Voltage & TEMperature)—used an Analog Devices voltage-to-frequency converter to transform analog measurements into audio pulses recorded by the cassette input.
Pricing then was modest—kits for about $40, assembled units $60—but the impact was wider than the cost: several hundred units were sold, a few overseas, and at least one made it into a space shuttle experiment as a temperature monitor (even when the main experiment didn’t go to plan). Alger’s story demonstrates how low-cost sensors + simple interfacing can turn a home microcomputer into a capable data-logger or robot sensor hub.
You can read more about Alger and the VOTEM here.
We talked robots
What started as a suggestion to “talk about robots” quickly evolved into a rich conversation connecting Timex/Sinclair machines (ZX81, TS1000) to early robotics projects, homebrew interfaces, and modern hardware hacks.
Bruce Taylor’s Henry robot—originally documented in Sync magazine—was a centerpiece of our retro-robotics discussion. Henry combined a ZX81/TS1000 (with a memory expansion) and custom interface electronics to control actuators, bump switches, and other sensors inside a plastic dome. Bruce’s design emphasized repurposed parts, simple relay and motor control, and real-world behavior like bump-and-reverse logic.
Key interface hardware included the RX81 board (an I/O interface that provided latched inputs and outputs) and expansion boards from small companies. In modern terms, RX81-equivalent functionality is what we now accomplish with microcontrollers and GPIO expanders.
We also took a deep dive into Hobby Robot’s robots—built from flower pots, drip trays, consumer speakers, and surplus motors. The designs reminded us that early hobby robotics often traded polish for cost-effectiveness. These projects showed that building a robot is often as much about creative sourcing and mechanical ingenuity as it is about electronics.
More details about robotics built using the Timex/Sinclair computers.
Carl Miles’ modern TS1000 reworking: expansion boards, audio, VGA, and RAM
Carl walked through his ambitious rework of the TS1000/ZX81 architecture. His goal: keep the original form factor while adding modern conveniences. Highlights include:
– Full-size keyboard case integration to replace membrane keyboards.
– Programmable joystick ports that can be remapped for older game and robotics software.
– ZX Wespy VGA generator using ESP32 to sniff video outputs and produce clean VGA output.
– Audio via AY-family chips (bringing the sound chip from the color machines to the TS1000), plus SD-card or Wi‑Fi-based file systems to avoid tapes.
– Massive memory expansions (hundreds of KB) and battery-backed RAM slots to preserve state without cassette hassles.
Carl is producing both a board that entirely replaces the original motherboard (fit into an original case) and an expansion board that sandwiches onto an existing TS1000 to add features like joystick ports, sound, and RAM. For robot builders, these kinds of expansions make old machines far more usable as controllers for sensors, motors, and modern peripherals.