# CPO3 Code Practice Oscillator Kit

INTRODUCTION Morse Code has been used since 1837. It was originally used for telegraph communications and was the first method used for radio communications. For many years, Morse Code was required knowledge for any shipboard radio operator. In 1910, the Titanic was the first ship to use the international distress call SOS. Until recently, code proficiency was required for all amateur radio licensees and was even required by the Boy Scouts. It still is required for the Signaling merit badge. The CPO3 is a fun, educational kit for any skill level builder and can be used to introduce anyone to this historic As the key is pressed, providing the circuit a ground path and starting the cycle, two things happen. C1 starts to charge via R1, R3 and R4. At this time the output of pin 3 is high. When the voltage on C1 reaches 2/3 of the supply voltage, the output of pin 3 will go low and pin 7 is grounded, starting the discharge cycle. The capacitor is discharged through R1. When the voltage on C1 reaches 1/3 of the supply voltage, the output at pin 3 goes high and pin 7 is no longer at ground. This starts the charging cycle again. Timing is completely independent of the supply voltage used. It is determined by the values R1, R3, R4 and C1. The formula for the total time (T) of a complete cycle is: T = 0.693[(R3+R4+2R1)C1]. The component values provided allow a range of 1300 Hz to 1700 Hz. The key is attached to pin 1 and provides the kit with a ground connection, completing the circuit and turning the entire unit on. The key is basically an on/off switch. Capacitor C2 filters out noise and R2 is a current limiting resistor for the speaker, SP1. Ramsey Customer Use Only Not For means of communication. CIRCUIT DESCRIPTION

Publication

CPO3  4