They definetely have a dealing desk!

Todays dealing desk is actually a buy / sell software that manages the orders sent to the bank.

The best way to know if a broker has a dealing desk is to ask him wether he allows scalping.

Non-dealing desk brokers would love you to scalp, and to do as many trades as possible (so they could earn the spread). They send your order straight away to the bank.

Dealing desk brokers (like IBFX) will not permit scalping, because their dealing desk tries to compensate the buy / sell orders from all the traders before sending any order to the bank. They can't deal with orders shorter than a couple of minutes.