299941
Sidetone in 19th century telephones varied until the carbon transmitter was used , which produced a distinct sidetone that discouraged speaking loudly enough , and occasionally so loud as to cause the instrument to produce uncontrolled oscillations , resulting in howling audio effects .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
 None