No not exactly - I'm talking about a device that attaches to say an MCCB (for example) as an accessory that acts as a tripping device when its control loop is opened (under voltage trip) - you would wire your N/C E-Stops to keep the unit energised and once the control loop is broken it would drop out the main MCCB. I maintain that this may not meet requirements depending on where your planning on using it - normally for schools you would bring all relevent circuits into a control board through a series of contactors or one main one with fusing down after, then use a safety relay to monitor the E-Stops and once activated it only kills the required circuits and not the whole board, resetting of the device also has to be discussed and normally should not be accessible for students to do so, so a key control is often used, this system is also favoured so the teacher can only energise it when he needs to so when absent the power is off to said outlets or loads, this stop students messing with machinery etc when no teacher is present.
