The instruction manual for 4mm neons indicates the Neon separator LED's are in series, as I understand it the side of the LED in which the ground is located has to be oriented in the same direction in a series circuit. I can't seem to determine what orientation (if any) would be required to get the circuit to work. Looking close at the LED doesn't help (see attached). If anyone could help clear this up for me I would appreciate it.
A quick note about the neons - although they are not polarized, only the negative electrode (cathode) will light. For both electrodes to light you must supply AC to the neon. You may wish to orient the neon tubes with the negative side facing the front for better viewing.