thanx friends!i see what i want,telephone line monitor&phone line indicator,but this i get a problem in language can some one translate in english pls!& on telephone line monitor i get a trouble where to connect the base leg of the transistor that in series with the speaker.&if some one could help me to analyse how the mathematical value of the components such as capacitor&resistor were obtained.and also how the circuit electronically works.pls help me im stack.