Digitized decoder-receiver for receiving call signal

Claim 1

A portable device for receiving a transmitted call signal containing a first digit and a second digit, said call signal being an electromagnetic wave that carries a specific sequence of pulses having a first pulse and a last pulse, and having been preassigned as a decimal number to a particular person(s), comprising: (a) a dc source for supplying power to said device; (b) antenna means for picking up said call signal once it has been transmitted; (c) an automatic gain control amplifier having an input terminal connected to said antenna means and at least one output terminal, said amplifier including means for converting said call signal, picked up by said antenna means, into a sequence of pulses; (d) decoder means for counting the number of pulses in said sequence of pulses and activating a specific output in accordance with said number of pulses, said decoder means having a set/reset terminal and a first input terminal connected to said output terminal of said automatic gain control amplifier; (e) a grounded-emitter transistor, having a base and a collector, for controlling said decoder means, said base of said transistor being connected to said output terminal of said automatic gain control amplifier and a first capacitor that cuts off said transistor at the end of said sequence of pulses, and said collector of said transistor being connected to said set/reset terminal of said decoder means for initializing said decoder means when said first pulse of said sequence of pulses reaches said input terminal of said decoder means; (f) a second capacitor which is charged when said first digit of said call signal is received and discharged when said second digit of said call signal is received; (g) an RC-integrating circuit having a time constant sufficiently longer than the time duration of said sequence of pulses that charge said second capacitor; (h) a controlled rectifier having a main current path and a second current path through a gate to said second capacitor, said output terminal of said decoder means charging said second capacitor through said main current path when said first digit of said call signal is received and discharging said second capacitor through said RCintegrating circuit when said second digit of said called signal is received; and (i) means for alarming said particular person(s), said means for alarming being connected in series with said second capacitor so that when said second capacitor discharges, said means for alarming is activated.