(a) When a vehicle is parked in any space adjacent to which a parking meter is located in accordance with the provisions of this chapter, the operator of such vehicle shall, upon entering the parking space, immediately deposit or cause to be deposited a ten-cent, five-cent, or one-cent coin, or coins of equivalent value that the Police Chief or Council may decide upon, in such parking meter, and put such meter in operation. No person shall fail to deposit such coin or coins of such specified values and put the meter in operation. Upon the deposit of such coin or coins of such specified values and placing such meter in operation, the parking space may be lawfully occupied by such vehicle during the period of parking time which has been prescribed for the part of the street in which such parking space is located. If the vehicle remains parked in any such parking space beyond the parking time limit fixed for such parking space, the parking meter shall, by its dial and pointer, indicate such illegal parking. In that event, such vehicle shall be considered as parked overtime and beyond the period of legal parking time.
(b) Commercial trucks may park in the parking meter zones to load or unload merchandise without depositing coins for a period not to exceed twenty minutes. No person shall park any commercial truck in any parking meter zone for longer than twenty minutes without depositing the required coins and putting the meter in operation.