Signals is a free and open source app that provides countdown and start signal sounds for sailing races. At present only Signals-Mobile for Android is available, but the laptop version is planned for release later this year.

The app should be available in the Google Play Store in the next few weeks, but can also be side-loaded from the source code repository (linked further down this page).

In this version, when connected to the USB cable of a phone or tablet it can send simple commands to a micro-controller (an Arduino for example) so that an electric horn can be triggered. If not connected, Signals just plays the sound of an air horn.

Standard sailing start sequences are available:

  • 5-4-1-Go
  • 10-5-Go

plus a training/utility sequence

  • 3-2-1-Go

Multiple starts can be set up with a 5 minute interval between starts (1 minute for the training sequence).

The sound signal can also be triggered manually by a button in the app for testing or for extra sailing race signals such as boat-over-the-line, general recall, shorten course or postponement.

For general recalls, a button in the app adds an extra start to the sequence during or after the countdown.

For automatic signals, the length of the signal is set to 1.5 seconds. For manual signals, the signal is as long as the button held down.

The characters sent over USB are “1” to start the sound signal and “0” to stop it at 9600 baud. The micro-controller must be set up to respond to these characters. Fortunately the code for this is not complicated and is available with the source code for the app itself (in the file main.cpp).


Source code is available at

The app was made with App Inventor



Setup page…

Countdown page…