RE: CNBC just announced issues with trading some London.stocks.19 Oct 2023 16:33
Dai,
Hopefully this explains the difference between SEAQ, SETS & SETSqx
Different stock exchanges have different systems to facilitate trading. To make matters more complicated, the same stock exchange can have a number of different systems for the trading of different securities – largely dependent on their levels of liquidity.
SEAQ (Stock Exchange Automated Quotation System)
SEAQ is essentially a computer-based system where all of the prices set by individual market makers are published, and where stockbrokers are able to find their clients the best price for a particular security. Some securities may have a dozen or more market makers, others may only have two. (AIM stocks)
SETS (Stock Exchange Electronic Trading Service)
Introduced in 1997, SETS is the London Stock Exchange’s flagship electronic order book. It is a further evolution from SEAQ. For instance, whereas SEAQ can be visualised as having brought together market makers on one screen – rather than them being stood on the floor of the stock exchange, serving brokers who served clients – SETS can be imagined as a ledger where everyone is free to enter bids and offers, which are matched if possible. The operation of SETS is automated and, as such, much more efficient.
(FTSE 100, 250)
SETSqx (Stock Exchange Electronic Trading Service – quotes and crosses)
Finally, SETSqx is a hybrid trading system, combining features from SEAQ and SETS, and is designed for securities with reasonable levels of liquidity, but which may at times require market maker quotes to maintain levels of trading. As such, the electronic order book is split into a quote book and an order book – the quote book being the listing of quotes by appointed market makers, and the order book being electronic orders entered as they are on SETS.