Mechanical placebo refers to a device or object that appears to perform a specific function, but in fact does nothing at all. 

“机械安慰剂”指的是看上去似乎能完成某种特定功能，但其实什么也做不成的装置或设备。

It is an impressive looking device or scheme, that in fact, does nothing. 

“机械安慰剂”的外观给人印象深刻，但其实毫无用处。

“机械安慰剂”的典型例子是电梯关门按钮和一些人行横道的步行按钮。这些按钮也称为“安慰按钮”。