Can the Hardy rate controller's remote function pause option be used as an interlock?

Can the Hardy rate controller remote function pause option be used as an interlock to prevent activation of the feeder before the process is ready? If so, can the switch between Pause and Ground safely be maintained (closed) until the process is ready?

The obsolete HI 2160 RC remote function input for PAUSE can stop the front display from starting the feeder. There is a scan time period cycle involved and could be a problem where the feeder would start if someone pressed the ON button. This would be a short pulse to the feeder and could be a safety concern. You need to lock out the keypad or add a physical interrupt to the feed motor when there is any human interaction with mechanical systems. You can also lock out the rate controller keyboard with Remote I/O (RIO) using a BTW59 with the stop bit locked ON.

With improved instruments, to eliminate that possibility of a pulse moving the feeder, a similar lock out method can be used with the HI 4060. 
The HI 4000 series command inputs only react to leading edge state changes.  (one shots) Keeping the pause or stop command input held high will not lock out the front keypad.  Using communications to hold a device in a certain state is a viable solution.  The command to set a bit is constantly set high.  Every time the front keypad is depressed the overriding command is sent and counters the button.  This locks the front keypad. 

For the HI4060 rate controller.
The HO3.8 Not OK to Feed signal will prevent the device from starting.  This is used as an Estop mode. 

Holding the ABORT input or bits high will lock the start function.   This command does not require the input to be leading edge.  As long as the abort input is held high, the NOK will stop the feeder from starting. 
The signal is TTL and shorting this signal for extended amounts of time is not a problem.   Keep the cable short as possible, do not exceed 50" and use shielded twisted pair cable.

Enabling a lock out for the Feeder Controller plug in modules is easier.  Your ladder logic has full control of the feeder.  Setting a signal at the HMI or I/O will do the job when properly programmed.