Royal Mail 4-State
The Royal Mail 4-State (RM4SCC, or CBC for "Customer Bar Code") bar code is used in mail sorting for the United Kingdom, in its Cleanmail service. The Dutch KIX barcode is a slight variant of this format. The UK postcode and delivery unit suffix are encoded along with a check digit.
This sort of bar code system is regarded as "four-state" because there are four types of bars, classified by presence of ascenders and/or descenders. This sort of system is transcribable using DAFT notation.