Various connectors are used for interconnecting electronic systems. The choice of connector depends mainly on the maximum frequency the cable is able to carry. Adapters are used to connect cables with different connectors; for example, a BNC-to-N adapter might be used to connect a frequency synthesizer to an oscilloscope. In-series couplers are used to connect cables with the same connectors. Terminators are used to make sure cables end in the correct impedance, to reduce reflection of the signal.