PTC Thermistor for Telecom Over-current Protection
Telecom PTC Thermistor Description
This series of ceramic 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 '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 tele 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 tele 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. We can manufacture a series of PTC thermistor fulfilling both requirements.
Typical Application of PTC Thermistor in Telecommunication Protection
Central Office Switching Equipment (C.O): analog and digital line cards, POTS, T1/E1 equipment, xDSL modems and splitters, multiplexers, CSU/DSU, servers.Primary Protection Modules: MDF (main distribution frame) modules, network interface devices (NIC).
Custom Premises Equipment, also known as subscriber terminal equipment (T.E.), IT equipment: Modem, sets, fax machines, wall outlet (plugs), alarm systems, answering machine, PBX systems, ADSL Splitters, internet appliance, POS terminals.
Access Network hardware, LAN WAN equipment, Powered Ethernet systems, VoIP (voice over IP equipment), integrated voice data (IVD), Set-top box (S.B), etc.
Telecom PTC Thermistor Features
Compliant with ITU-T K20 K21 K45
--Basic level lightning surges (10/700μs)Suitable for continuous connection to main voltage 110/230 VAC in tripped (high ohmic) condition.
--Basic level power Induction (600V,1A,0.2S)
--Power contact criteria A/B (230V,15min.)
Round leadless disk thermistor availble for combined usage of PTC and primary protection, e.g gas arrestor.
Typical Resistance @25C (R25) 10 ohm, 12 ohm, 18 ohm, 20 ohm, 25 ohm, 50 ohm, 55 ohm.
Matching available with narrow resistance tolerance.
Tight resistance tolerance maintained after switching.
Negligible resistance drift after soldering or switching.
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