How to disable a motor driver without disconnecting power?

My friend bought a CNC table that I'm helping him set up and learn to use. When the DC power supply for the motor drivers is plugged in the motors lock in place and nothing can be moved by hand. I'm wondering how to unlock the motor(s) for a given axis without turning off the power supply. The driver are DM542As with ENBL+ unconnected. It's my understanding that this is normal and that ENBL+ is held high internally. If I connect it to Common, maybe through a resistor, will that disable the driver & unlock the motors? If not, I suppose we could have switches to turn the power off to each individual axis's driver(s) to unlock the motors that way.

If you look at page four of the manual it shows how to connect an external switch for disable, the E+ would go to 5V and the E- would be taken to common (GND) through a N.O. switch to disable.
Al.

Thanks for the quick reply Al.

We didn't get a manual for the drivers. I found this, which has connection diagrams but nothing with actual switches. Everything I've seen indicates that if E+ is connected to 5V and E- to common the driver is enabled while connecting E+ to low disables the driver. Still not sure how leaving E+ unconnected still enables it, which is how it came from the company that sold the kit. The next time I work with the table, hopefully within the next few days, I'm going to check E+ for a voltage to see if there's something internal pulling E+ high and connect it to common through a resistor to try to free the motors.

With the input left unconnected it is the same as the opto/transistor/switch being open, if you connect the E+ to 5v and close the switch from E- to common, then the opto isolator is turned on, and the drive is disabled. This is the same way that the pulse/dir are activated, per page 4.
Al.