Abstract: A device comprising a RF transmitter, a casing for the RF transmitter and, connected to and extending from the RF transmitter, an antenna for radiating RF signals produced by the RF transmitter, the antenna comprising an elongated member having a first portion and a second portion each of which comprises a first conductor, a second conductor and an insulator between the first conductor and the second conductor, and, between the first portion and the second portion, a third portion comprising a first conductor, wherein the first conductor of each of the first portion, the second portion and the third portion is a common conductor connected to the RF transmitter and wherein the second conductor of the first portion and the second conductor of the second portion are electrically isolated from one another.

Abstract: A device comprising a RF transmitter, a casing for the RF transmitter and, connected to and extending from the RF transmitter, an antenna for radiating RF signals produced by the RF transmitter, the antenna comprising an elongated member having a first portion and a second portion each of which comprises a first conductor, a second conductor and an insulator between the first conductor and the second conductor, and, between the first portion and the second portion, a third portion comprising a first conductor, wherein the first conductor of each of the first portion, the second portion and the third portion is a common conductor connected to the RF transmitter and wherein the second conductor of the first portion and the second conductor of the second portion are electrically isolated from one another.

Abstract: An FSK demodulator is provided comprising means for receiving and digitizing an FSK signal (such as a signal comprising two frequencies f1 and f2 in which first and second logic states are represented by first and second periods of different durations). First, second, third and fourth consecutive transitions of the signal are identified and the times of said transitions are identified. A first period between the first and third transitions is calculated, as is a second period between the second and fourth transitions. A change of frequency in the signal is indicated when the first and second periods lie on opposite sides of a first threshold period (.tau.) and no change of frequency is indicated when the first and second periods lie on the same side of the threshold period (.tau.). In a further aspect of the invention, a transition is rejected as illegal when two consecutive transitions occur within a predetermined period of time.