external failsafe timer

例句：

1. 1. The external safety timer prevents the machine from starting until the temperature is within safe limits.
   外部安全计时器防止机器在温度未达到安全范围前启动。
2. 2. The manufacturer has included an external safety timer in the product to ensure that it doesn't start if thepower supply is interrupted.
   制造商已将外部安全计时器包含在产品中，以确保电源中断时它不会启动。
3. 3.The external safety timer is used to prevent the machine from operating when the operator is not present.
   外部安全计时器用于防止操作员不在时机器运行。