Home signals are stop signals, allowing a driver to proceed past the signal. These were used to keep trains apart by only permitting a train to pass when the line ahead is clear.
Distant signals provide train drivers with a warning about the home signals ahead. If the home signals are cleared then the distant signal can be cleared, advising the driver that he may proceed at normal speed. If the distant signal remains horizontal the driver knows that he must be prepared to stop and can begin to slow the speed of his train.
Combined home and distant signals were found in locations with short block sections, for example where two signal boxes control the separate ends of a station. The upper home signal arm cleared to allow a train to move up to the next section (eg to enter the platform), the lower distant signal arm advised the driver if signals of the next signal box have been cleared (eg if the signal at the end of the platform is or is not clear).