Polycom EF2201 Application Note page 6

Now, you should be able to send any valid EF Device command to the unit.
Here, a ***PING command has been sent to a EF2280 at a baud rate of 38400.
Note that by checking the L E option, that feature caused the PASSTHRU
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command to display double characters.
Without L E checked, here is the same window as displayed in Viewport.
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You do not have to use the L E option when sending commands;
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however, it makes sending commands easier since you can see what you've
typed locally.