The Radio Frequency Department of Vietnam said on Friday its technical team resolved the interference in Me Tri Thuong, Tu Liem Ward, Hanoi, tracing it to a wireless call-button system used at a coffee shop in the area.

The battery-powered buttons are designed to alert staff for table service, a setup increasingly common in cafes and restaurants across Vietnam.

The department said the device developed a technical fault and began transmitting at 433.91 MHz, a frequency band widely used by smart keys for cars and motorbikes.

The overlap caused signal interference, preventing vehicles from responding to their keys.

The wireless call buttons at a Hanoi coffee shop that interfered with smart keys. Photo courtesy of Vietnam’s Radio Frequency Department

The issue was resolved after the devices were powered down.

The agency said similar incidents have occurred in recent years, often involving malfunctioning or non-compliant wireless devices such as vibration alerts in cafes, rolling door remotes, and water pump switches.

Many of these products lack proper certification and are widely available on the market.

It advised individuals and businesses to use only certified radio-frequency devices with clear origins and regulatory approval marks.

Any similar interference issues should be reported promptly for investigation and resolution.