Reflector lamp unit of a bilaterally based discharge lamp and lamp holder

A reflector lamp unit for a bilaterally based discharge lamp having a lamp bulb, which comprises:

• a lamp holder;
• first and second terminal posts wherein the discharge lamp has a lamp bulb which is closed off in the direction of the longitudinal axis of the bulb for enclosing electrodes therein lying opposite one another and being electrically connected with said terminal posts;
• the holder including first and second mounting elements for respectively accommodating the terminal posts;
• and
• at least one coding element wherein at least one of the terminal posts has a slotted portion of a predetermined length and a predetermined lateral residual width, said at least one coding element having a coding slot open in a direction of insertion of the terminal posts wherein said coding slot has a width of a value substantially between the width of at least one of said terminal posts and the lateral residual width of the slotted portion of said at least one of said terminal posts;
• said at least one terminal post having said at least one coding member and is positioned in one of said first and second mounting elements;
• wherein the coding member comprises said coding slot which has a median line which runs parallel to the direction of the insertion of said at least one terminal post.