RTC Manufacturing Inc. AP21T Time Switch Controller

The RTC Manufacturing AP21T Time Switch Controller (models 99-001F and 99-009A; AP‑21 family) is a compact, single‑circuit, calendar‑programmable solid‑state time switch designed to switch electrical loads on a precise schedule. The AP21T is AC/DC powered, rated for a 15 A relay output, and supports program transfer between units (AP21T to AP21TR) to simplify distributed deployments. Programming is laptop‑based with the 21PC software, and the unit features a 16‑character alphanumeric LCD, daylight‑savings time automatic adjustment, and 48‑hour capacitive back‑up with no batteries. With dimensions of 2 in. x 2 1/2 in. x 4 in., it fits easily into standard cabinet spaces used in traffic infrastructure. The AP21T is designed for calendar‑based control of electrical circuits, including school‑zone flashers and other traffic‑control applications, providing reliable timed switching without the need for batteries. Its compact form factor and transfer capability make it straightforward to duplicate programs across multiple sites while maintaining exact timing across the system.