Signals is a free app that provides countdown and start signal sounds for sailing races.

  • Signals Android is available for phones and tablets
  • Signals Desktop is available for Windows, Macbook and other platforms

The Android app is available in the Google Play Store, or can be side-loaded from the source code repository (linked further down this page).

The Desktop version is intended for Windows and Macbook users (plus other platforms such as Raspberry Pi and Ubuntu). It is available at:

When connected to the USB cable of a phone, tablet or laptop the app can control:

    • a single channel USB relay (specifically an HW-667 or a number of the relays with a CH340 controller – see manual for more details)


    • a micro-controller (an Arduino for example)
Signals app countdown screen
Signals app connected to a portable race hooter

Start Sequences

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).

Manual Sound Signals

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.

Using An Arduino

You can program an Arduino (or similar micro-controller) to work with Signals. 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 for the Android app is available at

The Android app was made with App Inventor

Documentation (Android app)

Screenshots (Android app)

Setup page…

Countdown page…