Lost Model Alarm
by RMRC

Use this lost plane alarm between any servo channel that is regularly used. When it detects an inactive signal for more than 30 seconds, the alarm is activated. 

• Does not interrupt signal or power in servo wire.
• If circuit in alarm were to fail, servo will still be active.
• Works with any servo (analog or digital)
• Also works great as a reminder to un-plug your aircraft.