Ptc Thermistor

We are offering ptc thermistor for telecom over-current protection. Ptc (positive temperature coefficient ) thermistors help provide protection against power cross, power induction surges and lighting surge defined in itu, telcordia, ul. Available in chip, radial-leaded coated and non-coated, smd, twin vertical surface mount configuration. Ptc thermistor overcurrent protector provides reversible, self-resetting protection against over-currents of telecommunication line protector units, improve the reliability of custom premises and network equipment.
ceramic ptc thermistors can be found providing re-settable line protection at the exchange, monitoring hot spots and protecting ringers, battery feeds, transformers and relay circuits. Also used extensively to protect the mobile phone's battery pack against overcharging in land-based and radio mobile communications.
Advanced developments in telecom equipment in recent years have radically altered the protection requirements of both exchange and subscriber equipment. The ptc thermistor must protect the telephone line circuit against overcurrent, which may be caused by the following examples:
surges due to lighting strikes on or near to the line plant.
short-term induction of alternating voltage from adjactent power lines or railway systems, usually caused when these lines or systems develop faults
direct contact between telephone lines and power lines.
to provide good protection under such conditions, a ptc thermistor is connected in series with each line, usually as secondary protection; however, even with primary line protection (usually a gas discharge tube), the ptc thermistor must fulfill severe requirements.
surge pulses of upto 2kv can occur and in order to withstand short term power induction, the ptc thermistor must withstand high voltages. If the line has primary protection, a 220v to 300v ptc thermistor is adequate. Without primary protection, 600v ptc device is necessary.