Others would utilize exotic birds such as canaries which are able to hit the 2600 Hz tone to the same effect.

When not used, a 500 Hz tone is broadcast.

The most common form of this used a steady 2,600 Hz tone to identify a trunk as idle.

At 1 C, a 332.1 Hz tone has a 1-meter wavelength.

The top of the minute is marked by a 0.5 second 800 Hz tone.

In order to make free lines easy to find, the 2600 Hz tone was continually played into free trunks.

So long as the 2,175 Hz tone is present, the transmitter remains on.

Two of the pieces in each concert had 17 Hz tones played underneath.

"Yes; we should be hearing a 1650 Hz tone."

Such a group of gaps can only be generated by a 100 Hz tone.