Chromecast gets Guest Mode, now doubles up as dog whistling device

Ultrasonic pairing between Android and Chromecast devices will allow users to connect to Chromecast devices without first being on the same Wi-Fi network.

Google has announced that Chromecast's new Guest Mode now supports users not on the same Wi-Fi network as the device being used to cast content to TVs.

The feature, which is disabled by default, uses what Google calls a "special Wi-Fi beacon" to allow devices running Android 4.3 or greater to be aware of the Chromecast's presence. When a user taps on the Cast icon, a four-digit PIN needs to be verified to allow the Chromecast to stream the content.

The Chromecast will initially attempt to transfer the PIN using high-frequency tones, but, should the audio pairing fail, the user is able to see it displayed on-screen and enter the PIN by hand.

Teenagers, people with decent hearing, and pets, however, could be able to hear the PIN transfer process, Google said in its Guest Mode FAQ.

"Some people, particularly teenagers, are able to hear sounds in the ultrasonic range, and this may be what the person is hearing," the company said. "The ultrasonic token plays for only a short time each time your device is paired with a phone or tablet. You can disable guest mode at any time using the Chromecast app."

The search giant said that its use of ultrasonic tones will only allow people in the same room as the Chromecast to connect to it.

"Ultrasonic audio does not go through walls, glass, or even fabric. If the mobile device trying to connect to the Chromecast is not in the same room, it won't be able to hear the ultrasonic tones," the company said.

Guests using a Chromecast in Guest Mode will not be streaming content from their device to the Chromecast over mobile data, Google said, with the Chromecast using the Wi-Fi network that it is connected to when fetching content.

Users of iOS devices are not able to use Chromecast's Guest Mode.

Google said it will begin rolling out the update to Chromecast today.

In recent days, Google has announced the availability of the first stable release of Android Studio, an update to Android Wear, and the rolling out of an update to Android Lollipop.