| Home | Company Profile | Products Show | Technic Support | Contact Us 中 文
Products SPMZ2 Series

- SPMZA Series
- SPMZB Series
- SPMZC Series
- SPMZ2 Series
- SPMZ7 Series
- SPMZ8 Series

    A special case of overcurrent protection is PTC thermistors for telecommunication applications. Over voltage and current in telephone line can result from the following phenomenons:
    * surges due to direct lightning strikes or near to the line plant;
    * short-term induction of alternating voltage from adjacent power lines or railway systems , usually caused when these lines or systems develop faults;
    * direct contact between power lines and phone lines.
    Usually, there is a PTC thermistor connected in series with each line (see fig.1) as secondary protection. However, even with primary line protection (a gas discharge tube), the PTC thermistor must fulfill severe requirements. Because surge pulses will get up to 2 KV and in order to withstand such short-term power induction, the PTC thermistor must withstand high voltage. If the line has primary protection, a PTC thermistor withstand 200V-300V is enough;if not ,it must stand over 600V.


    They provide reversible, selfresetting protection against over current in central office, PBX, remote xDSL exchange, security unit and outdoor telephone.

Resistance at 25℃(Rn) Operating temperature range:25±2℃,within the allowable tolerance.
Operating temperature range:40±2℃,In static air for 30mi-nutes.Max.Voltage:60Vdc.Non-trip current energized time:60min. △R/Rn≤50%

Overcurrent operating

Operating temperature range:25±2℃. Voltage of power supply: 220Vrms.Test the time for the current decrease to limited value.

Overvoltage withstanding

Voltage of power supply: 265Vrms.Initial current: 3A.Energized time: 30min.After 4 hours in room temperature, test Rn. △R/Rn<20%.


Voltage of power supply: 220Vrms.Initial current: 3A.ON 60s,OFF 600S Cycle:30 times. After 4 hours in room temperature, test Rn. △R/Rn<20%.

Surge current

Current waves:10/1000S Min.Opening circuit voltage:1.0KV.Peak current:25A.Interval: 3min.Cycle: 30 times. After 4 hours in room temperature, test Rn. △R/Rn<20%.

Induction voltage

(Only for max.voltage more than 600V) Voltage of power supply: 650Vrms.Initial current: 1.1A.ON 2s,OFF 60S Cycle:10 times. After 4 hours in room temperature, test Rn. △R/Rn<20%.
Fail model Ⅰ:Voltage of power supply: 250Vrms.Initial current: 10 A.;Ⅱ:Voltage of power supply: 600Vrms.Initial current: 15A.;Ⅲ:Voltage of power supply: 650Vrms.Initial current: 10A.;Energized time: 30min. high resistance or open circuit is allowable, low resistance or firing is not allowed.
Restore time The necessary time of the resistance return to twice of Rn <60S。
Part Number Code
Go to Top

Tel: 86-755-26759829 26759929 Fax: 86-755-26759949 E-mail: spptc@spptc.com