This function indicates if the device does or does not exist.
Parameter: device
Type: string
Description: This is the house code and unit code or device code of the
device, such as "A1" or "q17".
Return value: status
Type: integer
Description: Returns -1
if the device does not exist, otherwise it returns the index number of
the device. The
index number can then be used with the GetDevice
function.