Mayday Uninterruptable Power Supplies
Mayday was a line of uninterruptible power supplies for the TRS‑80 and other computers. It was sold by Sun Research (originally Sun Technology), a division of Phase-R Corporation.
Phase-R Corporation was located in New Durham, New Hampshire and experienced frequent problems with poor power quality and frequent outages. They originally developed the Mayday to protect the office TRS‑80’s, describing it as “designed and developed using a complete TRS‑80 system.” Sun Research introduced the first Mayday model in 1980.
Sun Research sold several different Mayday models. All versions used a 12-volt car battery (enclosed in a special waterproof case) as the battery backup. The number of power outlets provided varied with the model, but ranged from two to eight. The price also varied, but a Mayday +S with a 150 watt power supply (suitable for a Model I) cost $325.
Just like a modern uninterruptible power supply, the Mayday provided protection against both brownouts and blackouts. In the event of a power outage, the Mayday could switch to battery power in less than 5 milliseconds. This was more than enough time to prevent memory loss or disk errors. Later Mayday models could even notify the computer through an I/O port if the power went out.
The amount of time a Mayday could run a computer entirely on battery power varied depending on the Mayday model and type of computer. According to one estimate, the Mayday +S could power a Model I for up to 30 minutes during a power outage.