[Phone Line Voltage]What is the phone line voltage is the phone line voltage safe?
The voltage in the phone line is 20V. When there is an incoming call, the telephone line voltage rises to 48V, and the phone rings. When off-hook to answer, the phone line voltage drops to 10V again.
Telephone lines are limited in current flow and fuses are installed before entering the cable. The switching equipment supplies power to each module when it comes out. The telephone line is powered by 48V, and the resistance is connected in series on the line. Each end is about 600 ohms. When the phone is ringing, the power consumption is the largest. The current of the normal call has been considered in the circuit design, and the average DC power of 48V per household does not exceed 20 mA. When a user end draws 100A of power for a long time, it will be monitored by the monitoring equipment, and the power will be automatically turned off for the user.
The current used program-controlled switchboard has a DC feed voltage of 48V. Since the lead-acid battery is floating, the actual voltage of the telephone is about DC 50V when it hangs up. When the phone is off-hook, the DC circuit of the phone is connected, and there is current in the phone. At this time, the voltage drop is 7-10V, depending on the length of the line and the phone.
The current after the phone goes off-hook is not the same, which is affected by the subscriber line, telephone and intra-office switching equipment. Generally at 20-30mA. The current should be around 5 microamps when on-hook.
When the bell rings, the ringing voltage is an AC voltage of 75V and a frequency of 16-25Hz.
The original vertical and horizontal switch is on-hook 60V;
The program-controlled switch is on-hook 48V;
The ring current voltage is 90V; Ring 90V, call 8V.
But the value is not exact and will vary within a certain range. What is given is only the general value of DC 48V when the local office hangs up.
Ringing: 20HZ, above 75V.
Call: It depends on the line and phone quality, generally between DC 6-12V.
Small switch: There are generally two types of DC voltage: 24 or 48.
The ringing is similar to that of a call.
Although the voltage is above 36V, it is not harmful to people because of its extremely small current. Don’t worry.
