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    SPMZB series PTC thermistors are used instead of conventional fuses to protect loads such as multimeter, transformers, intelligence-ammeter, and digital multimeter, etc. or electronic circuits against overcurrent, which is the third protective devices after "temperature fuse" and "temperature switch". They are also called "auto restore fuses" or "ten-thousand-time fuses".
    The operating principle is showed in the following figures, the PTC thermistor fuse connected in series with the load. When a circuit is in normal status, the current through PTC is no exceed the rated current and in normal state PTCR keep low resistance, which will not affect the normal operation of the protected circuit. In case of any trouble in the circuit and the current is greater than the rated value, the PTCR will become hot quickly and present as a high resistance state, which sets the circuit relatively "off" to protect the circuit from damage. After the trouble is removed, PTCR will automatically restore its low resistance state and the circuit will resume normal operation.

Part Number Code
Note :
1. The model with a * had been recognized by UL 1434(File#E236869).
2. The data is only for reference, you can forward your detailed requirements if possible.
3. We have obtained the SGS test report about the content of Lead、Cadmium、Mercury、 Hexavalent Chromium、PBBs、PBDEs in the SPMZB series PTCR.
Example I
SPMZB-6 20Ωtype of PTC thermistor is a kind of protective component applied in 485 Communication Interface, which evolutes from the remote XDSL security unit of the remote XDSL exchanges. The product is connected in series with 485 Communication Interface. It is so useful for protecting the interface against the damage of 220V alternating voltage caused by unexpected damage or damage artificially to the communication line. Also, it can properly reduce the influence of thunder and lightning reaction on the interface. The product has small resistance under room temperature, low rated electric-current, strong ability of bearing the voltage and fast response speed. So it is an economical and suitable choice to protect 485 Communication Interface.
Application circuit
Example II
SPMZB series of PTC thermistor is used for over-current protection, thermal protection and defending lightning strikes. It mainly assembles in the input end of the power of microcomputer抯 control panel of household appliances, apparatus and meter, communication line and equipment for overcurrent protection, thermal protection and defending lightning strikes. So is also called 揳uto restore fuse?and 搕en-thousand-time fuse? Due to the double sensitiveness to the temperature and electric-current, it can remedy the disadvantage of the temperature relay抯 non-sensitiveness to electric-current and normal fuse抯 non-sensitiveness to temperature. It has fast response speed, strong protection ability and high reliability. It is a kind of protective component of genuine quality and good price.
Application circuit

Example III
SPMZB-5 type of PTC thermistor for defending strikes on IC card seat is a new important application field developed successfully by our company recently. Its application in IC card seat has raised maximally the ability of defending strikes on read and write device of IC card, especially the ammeter抯 slot of IC card. It can bear static-electricity, dynamic-electricity, lightning strikes, short circuit and other various attacks. It provides practical and feasible tech-support to make our country popularize and universalize the consumer goods of advance payment as soon as possible.
Application circuit
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Tel: 86-755-26759829 26759929 Fax: 86-755-26759949 E-mail: spptc@spptc.com