Market makers use SEAQ to quote prices in a number of fixed interest securities, and execute deals non-electronically. Any firm listed on SEAQ must have at least two market makers willing to trade, one to buy and one to sell. All orders go through to the market makers.
SEAQ compares to the LSE's electronic order book known as Stock Exchange Electronic Trading Service (SETS), which automatically matches buyers and sellers electronically. This is where the most liquid stocks lie, as it is open to the public.