The Twist Online High Frequency UPS 1KVA TWUP1000/HF delivers stable backup power for servers, networking devices, and office equipment. It uses online double conversion technology for continuous clean power output. Additionally, the high-frequency design improves efficiency and reduces switching interruptions. Moreover, the UPS includes an LCD display for real-time monitoring and system status updates. It also features built-in 2x12V/9Ah batteries for backup operation during outages. Therefore, it protects connected devices from voltage fluctuations, surges, and power loss. Furthermore, the TWUP1000/HF supports pure sine wave output for sensitive electronic equipment. It also includes overload, short-circuit, and overheating protection for safer operation. Additionally, the compact tower design fits home, office, and IT environments easily. Specifications: 1KVA online double conversion UPS technology Built-in 2x12V/9Ah rechargeable batteries LCD display for system monitoring Pure sine wave output for stable power Overload and short-circuit protection system
PCE VX Online 1 KVA 800W Internal Batteries Double Conversion Online- Pure Sine Wave Model VX 1K Input Rating Voltage Frequency Voltage range Power Factor THDi 1000VA 220V, 230V, 240V, 1Ø 2Wires 40~70Hz 176-300 VAC at 100% load, 110-300 VAC at 50% load >99% <5% Ouput Active Power @ PF=0.9 Voltage (on battery) Frequency (on battery) Transfer Time Efficiency UPS Design Technology Output Wave Form Total Harmonic distortion (THD) Crest Factor 900W 220V, 230V, 240V, +/-1% (selectable output voltage), 1Ø 2Wires 50/60 Hz +/-0.2% 0 ms 93% Online double conversion design Pure Sinewave ≤3% (linear load), ≤5% (non linear load) 3:1 Protection Overload Protection Short Circuit Protection 110% for 10min, 130% for 1min, >130% for 3sec UPS output cuts off immediately using input fuse/circuit breaker protection System Display LCD indicators Load level, Battery level, AC mode, Battery mode, Bypass mode, and Fault indicators Alarm Battery mode Low battery Overload Fault Sounding every 4 second Sounding every second Sounding twice every second Continuously sounding Battery Battery Type Typical Recharge Time DC Voltage Charging Current Back up time(1/2 Load) 12V 9Ah 4 hours to 90% Full capacity 24VDC 1A 10~15 min depending on load Communication USB or RS-232 SNMP* Compatibility Interface with power management software Power Management from SNMP manager and web browser Supports Windows family, Linux, Unix and Mac Physical W x D x H mm Net Weight Kgs(lbs) 145x282x220mm 9.8Kg(21.6lb) Environment Operating Temperature Storage Temperature Altitude Audible noise Relative Humidity 0 – 40 °C / 32 ~ 104°F -20 ~ 50°C / -4 ~ 122°F 1,500 meters max <50dBA at 1 Meter 20 to 90% humidity (non-condensing) Standards & Certifications Performance Safety EMC (EMS / EMI) Design, production, & services Environment Marking & Certifications EN50091-3/IEC 62040-3 UL 1778, CE, EN 50091-1,EN 60950 (RD/), IEC 60950 IEC 61000-4-2/-3/-4/-5/-6/-8/-11, IEC 61000-3-2/-3,FCC Part 15, CISPR 22, EN 50091-2/IEC62040-2 Class A, EN 55022/B,FCC 47 part 15 – Subpart B – ISO 9001 ISO 14001 certified company CE, TUV/GS, UL, cUL, c-Tick
UPS PCE EXDC-2 MAX UPS Adapter for Cameras & Modems
The PCE PCD 12V 100Ah Deep Cycle Battery delivers strong and reliable power for many applications. It offers a larger 100Ah capacity for extended use. This helps engines, systems, and devices run longer between charges. Users experience dependable energy when needed most. Moreover, the PCE PCD Deep Cycle Battery uses a deep cycle design built for repeated discharge and recharge. It supports long-term use without damage. This increases the battery’s lifespan and reduces replacements. Performance remains consistent over time. In addition, the battery provides a stable 12 V output for balanced power delivery. It suits solar systems, RVs, marine setups, and backup power solutions. Power stays steady for lights and appliances. Daily use becomes more efficient. Furthermore, the PCE PCD 12V 100Ah Deep Cycle Battery features a rugged casing that protects internal cells. The strong build resists wear and harsh conditions. This helps maintain performance in many environments. Durability feels reassuring. Also, the battery supports deep discharge recovery for long service life. It recovers well after heavy use cycles. This improves energy storage and reliability. Users rely on strong power anytime. In addition, the PCE PCD Deep Cycle Battery is easy to install in compatible racks and holders. Connections stay secure and simple. Setup feels user-friendly for both beginners and professionals. Installation remains smooth. Furthermore, the PCE PCD Deep Cycle Battery performs steadily across varying temperatures. It stays reliable in moderate heat and cold. This makes it ideal for outdoor and mobile use. Overall, the PCE PCD 12V 100Ah Deep Cycle Battery delivers dependable power, long life, and robust performance. It fits homes, boats, RVs, and solar systems. This battery is perfect for users who want strong, lasting deep cycle energy every day. Specifications: Voltage : 12V Capacity : 100Ah
The Beco Mini DC UPS 8800mAh delivers compact and reliable power backup for small DC devices. It offers emergency power without bulky hardware. This helps protect devices during brief outages or unstable power. Users enjoy continuous operation with confidence. Moreover, the Beco Mini DC UPS features an 8800mAh battery for extended backup time. It supports devices like routers, cameras, and small electronics. This ensures continuous functionality when mains power fails. Backup power stays dependable. In addition, the DC UPS supports automatic switching when power cuts occur. It detects outages instantly and activates backup power without delay. This keeps your devices running smoothly. Protection remains seamless and reliable. Furthermore, the Beco Mini DC UPS includes stable DC output for sensitive electronics. Power delivery stays steady even under load. This helps reduce risk of damage. Devices operate without sudden stops. Also, the UPS delivers a compact and portable design for easy placement anywhere. You can install it near devices without taking much space. This adds convenience for small homes and offices. In addition, the Beco Mini DC UPS 8800mAh supports multiple connection options for flexible use. It works with DC devices requiring uninterrupted power. Also, the compact and sturdy casing improves durability for daily use. The build feels reliable and long‑lasting. Users can trust the UPS for regular backup needs. Overall, the Beco Mini DC UPS 8800mAh delivers dependable backup power, seamless switching, and flexible use in a compact form. It is ideal for small DC devices needing continuous power and stable operation. Specifications: MINI DC UPS POE 8800mah, 17W Built-in Lithium Battery 2200mAh*4 5VDC USB output, 3*Sockets DC output Interface 5V/9V/12V Over charge, Over discharge, Overload, & Short circuit protection Microprocessor controller guaranties high reliability Multi-LED Status Indicator For: Routers, CCTVs, Modem, Wireless Phones, Monitors, PSP, and others
The PROLINK Enerhome PRO2000 Line Interactive UPS is designed to provide reliable backup power and voltage protection for computers, networking equipment, and home electronics. It helps keep connected devices running during short power interruptions and unstable power conditions. The UPS provides a 2KVA capacity and uses Automatic Voltage Regulation (AVR) technology. Additionally, it helps correct voltage fluctuations and provides stable power output to improve equipment protection. The PROLINK PRO2000 features a line interactive design that allows quick switching to battery mode during power failures. Moreover, it provides efficient backup support for essential devices while reducing power-related risks. The UPS includes protection features against overload, short circuit, surge, and low battery conditions. Furthermore, these safety functions help protect connected equipment during different operating situations. The PROLINK Enerhome PRO2000 is suitable for homes, offices, and small workspaces that need dependable power backup. Therefore, it provides a practical solution for protecting computers, routers, and other important electronic devices. The compact design makes the UPS easy to install in different environments. In addition, its reliable performance helps users maintain stable operation during unexpected power interruptions. The PROLINK Enerhome PRO2000 2KVA Line Interactive UPS combines backup power, AVR voltage regulation, and protection features. As a result, it provides a reliable power solution for everyday electronic equipment. Specifications: Capacity: 2000VA / 1200W Technology: Line Interactive with AVR Protection: Overload, Short Circuit, Surge, Low Battery Protection Input Voltage: 220VAC Output Voltage: 220VAC
The Yuasa SWL2500T Industrial VRLA Battery delivers reliable power for industrial and backup applications. First, it provides consistent energy output for critical equipment and systems. In addition, the valve-regulated lead-acid (VRLA) technology ensures maintenance-free operation and extended service life. Moreover, the battery features durable construction, vibration resistance, and high discharge efficiency for demanding environments. The compact design allows easy installation in various setups. Finally, its dependable performance, safety features, and long-term reliability make it ideal for industrial, UPS, and emergency power systems. Specifications: VRLA Technology: Maintenance-free operation with long service life High Discharge Efficiency: Reliable power for critical equipment Durable Construction: Resistant to vibration and harsh environments Compact Design: Easy installation in various industrial setups Industrial Reliability: Ideal for UPS, backup, and emergency power
UPS ONLINE 3KVA 2400W 1 YEAR WARRANTY ABSOLUTELY PURE SINUSWELLE – With this inverter / inverter you operate your 220V devices via a 24V battery and a continuous power of 2400W 3KVA. Inverter is a device that allows you to use electrical devices everywhere, even when you are not at the power source MULTIFUNCTION HYBRID UNIT – Thanks to the small LCD display, it is also possible to charge the batteries with AC / solar charge controllers, setting the input voltage range and charging current. MODERN PROTECTION FEATURES – The device has many modern safety features such as: overload protection, overheating protection, short-circuit protection, so it is also suitable for home appliances, as well as microwaves, air conditioners, refrigerator, fan and daylight lamp. HIGH QUALITY MATERIALS – Equipped with PWM control, the inverter generates a pleasing amount of waste heat.
Features • Advanced DSP and 3-level technology • Output power factor 1.0 • Active power factor correction (APFC), input power factor up to 0.99 • High efficiency 95% (up to 98% in ECO mode) • Advanced digital parallel technology • Wide input voltage range (11 0 – 288 Vac) and frequency range (40 -70Hz) • 50 I 60 Hz frequency auto sensing • Two modes of frequency conversion: 50 Hz input I 60 Hz output or 60 Hz input I 50 Hz output • Dual-input design, supporting independent bypass • Flexible battery configuration (settable 16-20 pes batteries) • Digitally controlled charger • High charging current available (Max. 12 A) • Charging voltage and current configured by demands • Linear derating in low voltage input reducing battery discharging times, extending the service life of battery • Intelligent battery management, automatic floating I equalizing charge control, charger dormancy control, increasing battery life by 50%• Ability to switch on the UPS with batteries • Settable delayed start time when mains power is restored, reducing the impact on power grid or generator • Fan speed varies intelligently with temperature, reducing noise and extending its service life • Equipped with self-aging function • Compact internal layout, miniaturized the complete unit for small footprint • LCD+LED display, multi-functional keys operation, friendly human-machine interface • Powerful background software for parameters configuration • Advanced multi-platform communications: RS232, USB, RS485, SNMP and dry contacts communication interfaces • Effective software and hardware protection function, robust self-diagnostic function, and abundant event log for check Available Options • RS232 and smart card slot included • Optional parallel function, battery temperature compensation, SNMP card, USB, RS485 card, dry contacts, EMD, and SMS alarms Rear Panel 1. RS232 2. EPO 3. Parallel Port (optional) 4. USB (optional) 5. Temperature Detection (optional) 6. Intelligent Slot 7. Reserved: for manual bypass or battery breaker or outlets ect. 8.Fans 9. Bypass Breaker 10. Input Breaker 11.GND 12.Terminals and Cover http://en.eastups.com/EA900G4610kVA/6754.jhtml
The ProLink PRO910WL Professional II Series Online UPS is designed to provide stable and reliable power protection for servers, networking equipment, and critical electronic systems. It helps maintain continuous operation during power interruptions and protects connected devices from unstable electricity. The UPS provides a 10000VA capacity with an 8000W power rating. Additionally, it uses online double conversion technology to deliver clean and consistent power output for sensitive equipment that requires reliable energy support. The ProLink PRO910WL supports pure sine wave output for improved compatibility with different electronic devices. Moreover, its advanced power management system helps maintain stable voltage and frequency during changing power conditions. The UPS includes an LCD display that allows users to monitor important system information. Furthermore, the display provides details about input voltage, output voltage, battery status, load level, and operating conditions. The PRO910WL supports external battery configurations for extended backup time. In addition, it includes protection features against overload, short circuit, over-temperature, and battery-related issues to help protect connected equipment. The UPS is suitable for data centers, offices, industrial environments, and other locations that require dependable power backup. Therefore, it provides a practical solution for users who need continuous power protection for important systems. The ProLink PRO910WL Professional II Series Online UPS combines high power capacity, online protection technology, monitoring features, and safety functions. As a result, it delivers reliable backup power for critical applications. Specifications: Capacity: 10000VA / 8000W UPS Type: Online Double Conversion Output Waveform: Pure Sine Wave Display: LCD Display Protection: Overload, Short Circuit, Over Temperature, Battery Protection
INVO Online INH100 INVO Online INH100 Centralized server center, mainframe, network control center, computing center max efficiency UPS System . AC Input Bypass AC Output . Battery Fault Screen OFF ON LCD AC Input Bypass AC Output Battery Fault Screen OFF ON LCD INVO Online INH100 Full Specifications : INVO Online INH100 Centralized server center, mainframe, network control center, computing center INVO Online INH100 UPS High Frequency 1000 VA, LCD Display Inbuilt Battery 2 x 12V/9AH Specifications: Specifications : Centralized server center, mainframe, network control center, computing center INVO Online UPS High Frequency 1000 VA, LCD Display Inbuilt Battery 2 x 12V/9AH 1 year warranty Manufacturer Link
The PCE EX Online 6 KVA 5400W is a high-capacity online UPS built for strong power protection in offices and business environments. This UPS delivers clean and stable electricity even during severe power issues. Moreover, its true double-conversion design removes surges, sags, and spikes for safe device operation. Therefore, it fits companies and users who need dependable backup without interruption. First, the PCE EX Online 6 KVA 5400W supplies pure sine wave output for sensitive electronics like servers, workstations, and networking gear. This helps protect your devices from damage and performance drops. In addition, the online design ensures seamless switching between mains and battery power. As a result, connected equipment stays powered without sudden shutdowns during outages. Next, this UPS supports a high load capacity for multiple systems at once. You can run large setups including computers, storage units, and critical machinery. Furthermore, advanced battery management maximizes runtime and extends battery health. This means longer backup support when power cuts last. Meanwhile, the LCD display shows real-time status, load, and battery info for easy monitoring. The durable build quality makes the unit reliable for daily heavy use and long operational hours. Additionally, installation and setup are quick, with minimal steps required. Consequently, you save time and avoid complex configurations. Also, the UPS includes advanced safety features to prevent overloads and short circuits for extra peace of mind. Smart communication options integrate with software for automatic shutdown and alert notifications. This keeps systems protected even when you are away. Moreover, the UPS runs quietly and remains cool under full load without noise disruption. Therefore, it fits well in busy workspaces without distraction. Overall, the PCE EX Online 6 KVA 5400W delivers seamless power backup, strong protection, and stable performance. It provides great value for users who need reliable power security for critical systems. Specifications: Voltage : 220V, 230V, or 240V Capacity :12v/7Ah Frequency:50/60 Hz
APC UPS Accessories VGL9901I Easy UPS Dry Contact Card/Relay I/O card, 1 – 10KVA (SRV models)
Key Features Output Connections (1) IEC 60320 C19 Input Connections Schuko CEE 7 / EU1-16P Cord Length 8.2ft (2.5meters) Power Cord, C19 to CEE/7 Schuko, 2.5m Wide selection of Rack PDU power cords for a variety of IT equipment. Specifications : Output Overload Protection No Maximum Total Current Draw 16 Input Input frequency 50/60 Hz Acceptable Input Voltage 90 – 250VAC Number of Power Cords 1 Maximum Input Current 16A Maximum Line Current 16A Physical Net Weight 0.49lbs. (0.22KG) Shipping weight 0.66lbs. (0.3KG) Shipping Height 2.01inches (51MM, 5.1CM) Shipping Width 4.02inches (102MM, 10.2CM) Shipping Depth 7.99inches (203MM, 20.3CM) Color Black Environmental Operating Temperature 32 – 113 °F (0 – 45 °C) Operating Relative Humidity 0 – 95 % Operating Elevation 0 – 10000ft (0 – 3048meters) Storage Temperature -25 – 65 °C Storage Relative Humidity 0 – 95 % Storage Elevation 0 – 50000ft (0 – 15240meters) manufacturer link
APC UPS Accessories SURT192RMXLBP2 APC Smart-UPS RT192V RM 15/20KVA SURT models Battery Pack 2 Rows
PROLINK 2KVA AUTO VOLTAGE REGULATOR W/LCD PVR2000D PROLiNK PVR Series is designed to automatically maintain a constant voltage level to protect sensitive electronics from brownouts, under voltages and over voltages. The PROLiNK PVR takes efficiency to a new level with its microprocessor controller tailored to allow extremely fast response for detecting and regulating voltage. Equipped with a time-delay function, the PVR is able to protect connected devices from power-back surges.
Specifications : Le grand ups keor spx 800va 310301 1year warranty ups 800va
UPS battery 12V 7A Battery for UPS 7A 12v
Max Configurable Power (Watts) 6.0kWatts / 6.0kVA Efficiency at Full Load 94.0 % Output Frequency (sync to mains) 50/60 Hz +/- 3 Hz Sync to mains Other Output Voltages 220 V, 240 V Load Crest Factor 3 : 1 Topology Double conversion online Waveform type Sine wave Bypass Internal bypass (automatic and manual) Input Input frequency 40 – 70 Hz Input voltage range for main operations 110 – 300 Adjustable (half load), 176 – 300V Efficiency at Full Load 94.0 % Other Input Voltages 220 V, 240 V Batteries & Runtime Battery type Lead-acid battery Typical recharge time 3hour(s) Battery Charge Power (Watts) 373 Watts Runtime View Runtime Graph View Runtime Chart Communications & Management Interface Port(s) DB-9 RS-232, Intelligent Smart Slot, USB Control panel Multifunction LCD status and control console Audible Alarm Alarm when on battery : distinctive low battery alarm : overload continuous tone alarm Emergency Power Off (EPO) Yes Available SmartSlot™ Interface Quantity 1 Surge Protection and Filtering Surge energy rating 600Joules Physical Maximum Height 685MM, 68.5CM Maximum Width 190MM, 19.0CM Maximum Depth 374MM, 37.4CM Net Weight 54.0KG Shipping weight 66.0KG Shipping Height 910MM, 91.0CM Shipping Width 290MM, 29.0CM Shipping Depth 495MM, 49.5CM Color Black Environmental Operating Temperature 0 – 40 °C Operating Relative Humidity 0 – 95 (Non-condensing) % Operating Elevation 0 – 3000meters Storage Temperature -15 – 60 °C Storage Relative Humidity 0 – 95 (Non-condensing) % Storage Elevation 0 – 15000meters Audible noise at 1 meter from surface of unit 55.0dBA Protection Class IP20 1 YEAR WARRANTY
Description : The Professional Series (1P/1P) – Tower is an advanced, affordable on-line double-conversion technology single-phase UPS system. Tower versions are available with 1000VA to 10000VA models and these offer high reliability for workstations, server and network equipment. The Professional Series is designed with automatic voltage regulation (AVR) to protect against power outages, disturbances and spikes. High voltage battery chargers and battery extension assembly is available for the long run time application. Key Features and Benefits True Double-Conversion Online UPS Mircoprocessor control optimizes reliability Input power factor correction Output Power Factor 0.80. Wide input voltage (110V – 300V) Converter mode available ECO mode for enegry saving (Only available for 1 – 3 KVA) Generator compatible Adjustable battery number only available for 6K and up models Smart SNMP works well with either USB or RS-232 together Emergency power off function (EPO) only available for 6K / 10K models Optional isolation transformer available. 02 Years Warranty manufacturer link
Specifications : UPS Type Tower Phase Single phase with ground Rating (VA) 10000 Nominal Power (W) 8000 Standard ModelDimension (mm) 442 x 190 x 688 (D x W x H) Weight (kg) 66 Long-run ModelDimestions (mm) 442 x 190 x 318 (D x W x H) Weight (kg) 16 INPUT Connection Type Terminal Nominal Voltage 208/220/230/240VAC Voltage Range 110-300 VAC (Load at 50%)176-300 VAC (Load at 100%) Frequency Range 46~54 Hz or 56~64 Hz Power Factor >= 0.99 OUTPUT Connection Type Terminal Output Voltage 208/220/230/240VAC Voltage Regulation ±1% Frequency Range (Synchronized Range) 46~54 Hz or 56~64 Hz Frequency Range (Batt. Mode) 50Hz or 60Hz +/-0.1Hz Current Crest Ratio 3:1 Harmonic Distortion ≤3% THD (Linear load)≤5% THD (Non-linear load) ALARM & INDICATORS Battery Mode Sounding every 4 seconds Low Battery Sounding every second Overload Sounding twice every second Fault Continuously sounding LCD Load level, Battery Level, AC mode, Battery mode, Bypass mode and Fault CONNECTIVITY, CONTROL & MONITORING Front panel Status LED, Function keys, LCD display Communication Smart RS232*USB Port Emergency Power Off (EPO) BATTERY Standard ModelType 12V / 9Ah Numbers 16 Typical Recharge Time 9 hours recover to 90% capacity Long-run ModelType Depending on the capacity of external batteries Number 16 ~ 20 (Adjustable) Charging Current (max) 1A/2A/4A/6A (Adjustable, 6A is only available for 16pcs batteries) manufacturer link
Specifications : Le grand ups keor spx 2kva 2000va 1200w ups 2kva 1 year warranty
PCE EX Online 2 KVA 1800W is a double-conversion online UPS designed to deliver continuous and stable power protection for computers, servers, and sensitive electronic equipment. It ensures uninterrupted operation during outages and unstable voltage conditions. In addition, PCE EX Online 2 KVA 1800W uses true online double-conversion technology. Therefore, it provides zero transfer time between mains and battery mode. Moreover, it delivers a pure sine wave output for safe and stable power to connected devices. Furthermore, PCE EX Online 2 KVA 1800W supports a 2kVA / 1800W load capacity. As a result, it can handle multiple devices such as PCs, routers, and small servers. It also maintains stable voltage regulation for sensitive workloads. In addition, PCE EX Online 2 KVA 1800W includes advanced protection features. Therefore, it helps protect against overload, short circuits, and power fluctuations. Moreover, it is designed for consistent performance in professional and office environments. Overall, PCE EX Online 2 KVA 1800W delivers reliable, uninterrupted, and high-quality backup power for critical systems. Specifications: 2kVA / 1800W power capacity for multiple devices Online double-conversion UPS technology Zero transfer time for uninterrupted power Pure sine wave output for safe device operation Protection against overload and voltage fluctuations
Specifications : GENERAL Rated Power 5000VA / 5000W Communication Interface Removable USB / RS232 / RS485 / Bluetooth / Dry-contact Dimension D x W x H (mm) 115 x 300 x 400 Net Weight (kgs) 13 INPUT Voltage 230VAC Selectable Voltage Range 170 ~ 280 VAC (For Personal Computers)90 ~ 280 VAC (For Home Appliances) Frequency Range 50Hz / 60Hz (Auto sensing) OUTPUT AC Voltage Regulation (Batt. Mode) 230VAC ± 5% Surge Power 10000VA Efficiency (Peak) 90% ~ 93% Transfer Time 15 ms (For Personal Computers)20 ms (For Home Appliances) Waveform Pure sine wave BATTERY Battery Voltage 48VDC Floating Charge Voltage 54VDC Overcharge Protection 63VDC SOLAR & AC CHARGER Solar Charger Type MPPT Maximum PV Array Open Circuit Voltage 500VDC Maximum PV Array Power 5000W MPP Range @ Operating Voltage 120VDC~450VDC Maxmum Solar Charge Current 100A Maximum AC Charge Current 100A manufacturer link
The Twist Online High Frequency UPS 3KVA TWUP3000/HF delivers reliable backup power for servers, networking systems, and professional equipment. It uses online double conversion technology for continuous clean power output. Additionally, the high-frequency design improves efficiency and reduces power interruption risks. Moreover, the UPS includes an LCD display for real-time system monitoring and status alerts. It features internal 6x12V/9Ah batteries for backup operation during outages. Therefore, it helps protect sensitive devices from voltage fluctuations and sudden power loss. Furthermore, the TWUP3000/HF supports pure sine wave output for stable performance with critical equipment. It also includes overload, short-circuit, and overheating protection for safer operation. Additionally, the compact tower design fits office, server room, and IT environments easily. Specifications: 3KVA online double conversion UPS technology Internal 6x12V/9Ah rechargeable batteries LCD display for real-time monitoring Pure sine wave output for stable power delivery Overload and short-circuit protection system