An antenna switch circuit for use in a RF transceiver, the antenna switch circuit comprising: (xix) a transmitter terminal for receiving an input RF signal from a transmitter; (xx) a receiver terminal for providing an output RF signal to a receiver; (xxi) an antenna terminal for providing an output RF signal to an antenna and for receiving an input RF signal from an antenna; (xxii) a transmission transfer path for transferring a RF signal from the transmitter terminal to the antenna terminal when the switch circuit is in a transmit mode; (xxiii) a reception transfer path for transferring a RF signal from the antenna terminal to the receiver terminal when the switch circuit is in a receive mode; (xxiv) in a first of said transfer paths a first electrically controlled device having a conducting state and a blocking state, the electrically controlled device in its blocking state in a first mode of the switch circuit isolating a second of the transfer paths; (xxv) in the second of the transfer paths an isolator which isolates the first transfer path in a second mode of the switch circuit; and (xxvi) a second electrically controlled device having a conducting state and a blocking state and operable in its conducting state to connect one of the transfer paths to ground; and characterised in that the antenna switch circuit further includes: (xxvii) at least one further electrically controlled device having a conducting state and a blocking state; wherein the electrically controlled devices are arranged in the circuit to protect the transmitter terminal from discharge of both positive and negative electrostatic charge. Also described are a RF transceiver incorporating the antenna switch circuit and a method of protecting a RF transmitter from electro-static discharge using the antenna switch circuit.
