How much voltage comes up in the telephone lines present in our home?

When the telephone is NOT in use (on hook) the voltage across the two wires (tip and ring) is about 48 volts D.C. When the telephone IS in use (off hook) the voltage across the tip and ring wires drops to about 6 volts D.C. When a ringing signal is being sent there is an A.C. voltage "superimposed" on top of the normal D.C. voltage. This "ringing voltage" is nominally about 90 volts at 20 Hertz (cycles) but could be as high as 130 volts and at different frequencies.

48 volts DC standard. When in use up to 90 volts AC

If you are hoping to use the lamp as a visual indicator of when the phone rings, the ring voltage is AC. It would cost you more to buy the parts you needed than to just buy a visual alerting product for the hearing impaired. www.sandman.com But to answer your original question, phone lines are considered to be DC voltage. This is because most landline telephone companies are government regulated, thus required to provide as close as possible to 99.999 up-time each year. To accomplish this large battery systems (called DC plants) are kept on-site to power the telco equipment incase of commercial power failures. All batteries are DC, thus the line power is DC. Telco lines do use some AC power on the line, but this is only used to "ring" the subscribers line.

It depends on the phone company but about 5 V d.c is common. Higher voltages would be too dangerous for normal use.

30-50v dc