<P> The development of the APCO Ten Signals began in 1937 to reduce use of speech on the radio at a time when police radio channels were limited . Credit for inventing the codes goes to Charles `` Charlie '' Hopper , communications director for the Illinois State Police , District 10 in Pesotum , Illinois . Hopper had been involved in radio for years and realized there was a need to abbreviate transmissions on State Police bands . Experienced radio operators knew the first syllable of a transmission was frequently not understood because of quirks in early electronics technology . Radios in the 1930s were based on vacuum tubes powered by a small motor - generator called a dynamotor . The dynamotor took from 1 / 10 to 1 / 4 of a second to `` spin up '' to full power . Police officers were trained to push the microphone button , then pause briefly before speaking ; however , sometimes they would forget to wait . Preceding each code with `` ten - '' gave the radio transmitter time to reach full power . An APCO Bulletin of January 1940 lists codes assigned as part of standardization ; </P>
<P> The development of the APCO Ten Signals began in 1937 to reduce use of speech on the radio at a time when police radio channels were limited . Credit for inventing the codes goes to Charles `` Charlie '' Hopper , communications director for the Illinois State Police , District 10 in Pesotum , Illinois . Hopper had been involved in radio for years and realized there was a need to abbreviate transmissions on State Police bands . Experienced radio operators knew the first syllable of a transmission was frequently not understood because of quirks in early electronics technology . Radios in the 1930s were based on vacuum tubes powered by a small motor - generator called a dynamotor . The dynamotor took from 1 / 10 to 1 / 4 of a second to `` spin up '' to full power . Police officers were trained to push the microphone button , then pause briefly before speaking ; however , sometimes they would forget to wait . Preceding each code with `` ten - '' gave the radio transmitter time to reach full power . An APCO Bulletin of January 1940 lists codes assigned as part of standardization ; </P>
where does the term ten four come from
where does the term ten four come from
APCO Ten Signals
APCO Ten Signals