If it is a Duplex it will have a TT relay (Transfer Time). If no TT it is a 2 car Group. If it is a Duplex look at HJG relay (Higher Demand for Hall) and there should be a HLR contact in there that can hold car. (HLR is home landing relay in at lobby). If it's a 2 car group it will use a Selected Car System which allows only one car to dispatch from lobby for a period of time unless loaded. The SC system only allows one hall lantern to light for the next car being dispatched.