Abstract: A signal switch and combining system for a radio communication system having two receivers (R.sub.A, R.sub.B) includes a comparator operable to determine which of the receiver output signal to noise ratios is the greatest at any instant. There is also a threshold detector arranged to determine when the difference between the two signal to noise ratios exceeds any one or more of a number of predetermined threshold levels. A gating network (GN) responds to the outputs of the comparator and threshold detector (CT) to control a switching and impedance network SZ. This controls the connection of ratio signals from the two receivers (R.sub.A, R.sub.B) to an output load. The network is arranged to connect to the load either one of the two radio signals or a combination of the two signals in one of a number of predetermined ratios. The signal to noise ratios of the two receiver output signals are conveniently indicated by the receiver automatic gain control signals.