One classic set you’ll see in most vintage mystery movies is an interrogation room with a “two-way” mirror in one wall. This cool gadget lets the witnesses see the suspects from another room while the ...

It’s a familiar scene from every police procedural: In one brightly lit room, a perp is being questioned. In an adjacent room ...

TikTok is full of people “discovering” spy mirrors in their hotel rooms and Airbnbs. Or, more often, they use a normal hotel mirror to demonstrate a trick that supposedly reveals such mirrors.

Recently (5/21/25), I published a Design Idea (DI) describing a bidirectional current mirror using just two transistors and a diode, “A two-way mirror—current mirror that is.” That circuit works well ...