A security system, comprising at least a first handheld device, a second handheld device, a first secure entity, and a second secure entity, wherein:—
- a) said first handheld device and said first secure entity are electronically pre-registered with each other, said first handheld device and said second secure entity are electronically pre-registered with each other, said second handheld device and said first secure entity are electronically pre-registered with each other, and said second handheld device and said second secure entity are electronically pre-registered with each other, with pre-registration of each respective handheld device and secure entity pair establishing a unique channel for the respective handheld device and secure entity pair;
- b) each said unique channel is configured to allow two-way communication by encoded wireless signals between the respective handheld device and secure entity pair;
- c) the encoded wireless signals are of radio frequency;
- d) the encoded signals include a first request signal emitted from the handheld device intended for the secure entity of the respective handheld device and secure entity pair, and a second feedback signal emitted from the secure entity intended for the handheld device of the respective handheld device and secure entity pair, with the second feedback signal generated only in response to the first request signal and actionable by the handheld device of the respective handheld device and secure entity pair and not the other handheld device or other handheld devices;
- e) each said first request signal and said second feedback signal in response contains digital coding of at least a first part, a second part and a third part;
- f) the first part coding of the first request signal represents an identification of said handheld device of the respective handheld device and secure entity pair, the second part digital coding of the first request signal represents a channel code designated in said handheld device with respect to said secure entity of the respective handheld device and secure entity pair, and the third part coding of the first request signal represents an instruction from said handheld device to said secure entity of the respective handheld device and secure entity pair;
- and
- g) the first part coding of the second feedback signal represents an identification of said secure entity of the respective handheld device and secure entity pair, the second part coding of the second feedback signal represents a channel code designated in said secure entity with respect to said handheld device of the respective handheld device and secure entity pair, and the third part coding of the second feedback signal represents an instruction from said secure entity to said handheld device of the respective handheld device and secure entity pair.