Dual-circuit telephony

A telephone instrument comprising:

• means for providing signals for transmission;
• means for converting said signals received by the instrument into output signals;
• means for selectively establishing and terminating a connection between another telephone instrument by way of a circuit-switched telephone network and for selectively establishing and terminating a connection between the instrument and a packet-switched communication network;
• and
• control means operable:
• (i) to signal over the circuit-switched network a request to said another instrument for a network address on the packet-switched network;
• (ii) in response to receipt of an acknowledgement signal including a network address for said another instrument to establish a connection to the said other instrument by way of said packet-switched network;
• (iii) on receipt of a call by way of the circuit-switched network to provide an acknowledgement including the network address of the instrument.
• (iv) on receipt of a consequent message over the packet-switched network to terminate connection to the circuit-switched network and to transfer the call to the packet-switched network connection;
• and
• (v) detect temporary silence in the call connection over at least the circuit-switched network before terminating the call connection over the circuit-switched network.