Sentence examples for a signal from inspiring English sources

"a signal" is a perfectly correct and usable phrase in written English.
You can use it when you want to describe an object or gesture that conveys information or communication. For example: - The teacher gave the students a signal to start the test. - She sent me a signal with her eyes to let me know it was time to leave. - The captain raised the flag as a signal for the team to begin the race. - My phone received a weak signal, so I couldn't make a call. - I followed his hand signals as we navigated through the crowded streets. - The flashing lights on the dashboard were a signal that something was wrong with the car.