Firepower 70xx Family Appliances
This section describes the power requirements for:
- Firepower 7010, 7020, and 7030 (CHRY-1U-AC)
- Firepower 7050 (NEME-1U-AC)
These appliances are suitable for installation by qualified personnel in network telecommunication facilities and locations where the National Electric Code applies. Note that each is available only as an AC appliance.
Cisco recommends that you save the packing materials in case a return is necessary.
For more information, see the following sections:
- See Installation for circuit installation, voltage, current, frequency range, and power cord information.
- See Grounding/Earthing Requirements for bonding locations, recommended terminals, and ground wire requirements.
Installation
This appliance must be installed in accordance with the requirements of Article 250 of NFPA 70, National Electric Code (NEC) Handbook, and local electrical codes.
The appliance uses a single power supply. An external surge protection device must be used at the input of the network equipment where the Firepower System is to be installed.
The circuit must be rated for the full rating of the appliance.
Voltage
The power supply works with 100VAC to 240VAC nominal (90VAC to 264VAC maximum). Use of voltages outside this range may cause damage to the appliance.
Current
The labeled current rating is 2A maximum over the full range. Appropriate wire and breakers must be used to reduce the potential for fire.
Frequency Range
The frequency range of the AC power supply is 47 Hz to 63 Hz. Frequencies outside this range may cause the appliance to not operate or to operate incorrectly.
Power Cord
The power connection on the power supply is an IEC C14 connector and accepts IEC C13 connectors. A UL-recognized power cord must be used. The minimum wire gauge is 16 AWG. The cord supplied with the appliance is a 16 AWG, UL-recognized cord with NEMA 515P plug. Contact the factory about other power cords.
Note
Do not cut the cord on the power supply.
Grounding/Earthing Requirements
The appliance must be grounded to the common bonding network.
Bonding Location
A ground bonding location is provided on the rear of the chassis. An M4 stud is provided. An outside-toothed lock washer is provided for attaching a ring terminal. A standard ground symbol is available by each stud.
The following illustration indicates the bonding location on the chassis.
Recommended Terminals
You must use a UL-Approved terminal for the ground connection. A ring terminal with a clearance hole for #6 (M3.5) stud may be used. For 16 AWG wire, AMP/Tyco 36151 is recommended. This is a UL-approved ring terminal with a hole for a #6 stud.
Ground Wire Requirements
The ground wire must be sized sufficiently to handle the current of the circuit in case of a single fault. The size of the ground wire should be equal to the current of the breaker used to protect the circuit. See Current.
Bare conductors must be coated with antioxidant before crimp connections are made. Only copper cables can be used for grounding purposes.
Firepower 71xx Family Appliances
This section describes the power requirements for:
- Firepower 7110 and 7120 (GERY-1U-8-AC)
- Firepower 7115 and 7125 (GERY-1U-4C8S-AC)
These appliances are suitable for installation by qualified personnel in network telecommunication facilities and locations where the National Electric Code applies. Note that each is available only as an AC appliance.
Cisco recommends that you save the packing materials in case a return is necessary.
For more information, see the following sections:
- See Installation for circuit installation, voltage, current, and frequency range, and power cord information.
- See Grounding/Earthing Requirements for bonding locations, recommended terminals, and ground wire requirements.
Installation
The Firepower System must be installed in accordance with the requirements of Article 250 of NFPA 70, National Electric Code (NEC) Handbook, and local electrical codes.
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each one must be rated the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different 220V circuit. Each circuit must be capable of supplying 5A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same 220V circuit. The maximum draw from this circuit would be 5A, as stated on the label.
Voltage
The power supplies will work with these voltages: 100VAC to 240VAC nominal (85VAC to 264VAC maximum). Use of voltages outside this range may cause damage to the appliance.
Current
The labeled current rating for each supply is: 10A maximum over the full range, per supply 5A maximum for 187VAC to 264VAC, per supply. Appropriate wire and breakers must be used to reduce the potential for fire.
Frequency Range
The frequency range of the AC power supply is 47 Hz to 63 Hz. Frequencies outside this range may cause the appliance to not operate or to operate incorrectly.
Power Cords
The power connections on the power supplies are IEC C14 connectors and they will accept IEC C13 connectors. A UL-recognized power cord must be used. The minimum wire gauge is 16 AWG. The cords supplied with the appliances are 16 AWG, UL-recognized cords with NEMA 515P plug. Contact the factory about other power cords.
Grounding/Earthing Requirements
The Firepower System must be grounded to the Common Bonding Network.
Bonding Locations
Ground bonding locations are provided on the rear of the chassis. M4 studs are provided. Outside-toothed lock washers are provided for attaching ring terminals. A standard ground symbol is available by each stud.
The following illustration indicates the bonding locations on the chassis.
Recommended Terminals
You must use UL-Approved terminals for the ground connection. Ring terminals with a clearance hole for 4mm or #8 studs may be used. For 10-12 AWG wire, Tyco 34853 is recommended. This is a UL-approved, ring terminal with a hole for a #8 stud.
Ground Wire Requirements
The ground wire must be sized sufficiently to handle the current of the circuit in case of a single fault. The size of the ground wire should be equal to the current of the breaker used to protect the circuit. See Current.
Bare conductors must be coated with antioxidant before crimp connections are made. Only copper cables can be used for grounding purposes.
Firepower 81xx Family Appliances
This section describes the power requirements for:
- Firepower 8120, 8130, and 8140 (CHAS-1U-AC, CHAS-1U-DC, or CHAS-1U-AC/DC)
These appliances are suitable for installation by qualified personnel in network telecommunication facilities and locations where the National Electric Code applies.
Cisco recommends that you save the packing materials in case a return is necessary.
For more information, see the following sections:
- See AC Installation for circuit installation, voltage, current, and frequency range, and power cord information.
- See DC Installation for circuit installation, voltage, current, ground references, terminals, breaker requirements, and minimum wire size.
- See Grounding/Earthing Requirements for bonding locations, recommended terminals, ground wire requirements, and DC supplies.
AC Installation
The Firepower System must be installed in accordance with the requirements of Article 250 of NFPA 70, National Electric Code (NEC) Handbook, and local electrical codes.
Caution
Do
not connect DC power to AC supplies.
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each one must be rated the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different 220V circuit. Each circuit must be capable of supplying 5A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same 220V circuit. The maximum draw from this circuit would be 5A, as stated on the label.
AC Voltage
The power supplies will work with these voltages: 100VAC to 240VAC nominal (85VAC to 264VAC maximum). Use of voltages outside this range may cause damage to the appliance.
AC Current
The labeled current rating for each supply is: 5.2A maximum over the full range, per supply 2.6A maximum for 187VAC to 264VAC, per supply. Appropriate wire and breakers must be used to reduce the potential for fire.
Frequency Range
The frequency range of the AC power supply is 47 Hz to 63 Hz. Frequencies outside this range may cause the appliance to not operate or to operate incorrectly.
Power Cords
The power connections on the power supplies are IEC C14 connectors and they will accept IEC C13 connectors. A UL-recognized power cord must be used. The minimum wire gauge is 16 AWG. The cords supplied with the appliances are 16 AWG, UL-recognized cords with NEMA 515P plug. Contact the factory about other power cords.
DC Installation
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Caution
Do
not connect AC power to DC supplies.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each circuit must be rated to the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different –48VDC circuit. Each circuit must be capable of supplying 20A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same –48VDC circuit. The maximum draw from this circuit would be 20A, as stated on the label.
Caution
Use of this optimization requires that the power cords are rated for the full rating for each supply.
DC Voltage
The power supplies will work with these voltages:
- -48VDC nominal referenced to RTN
- -40VDC to -72VDC maximum
Use of voltages outside this range may cause damage to the appliance.
DC Current
11A maximum, per supply
Ground Reference
The DC power supplies are fully isolated from the ground reference.
Recommended Terminals
Power is connected to the DC supplies through screw terminals. Terminals must be UL approved. Terminals must have a hole supporting an M4 or a #8 screw. The maximum width of the terminal is 8.1mm (0.320”). A representative spade terminal for 10-12 gauge wire is Tyco 325197.
Breaker Requirements
A breaker sufficient to carry the rated current at the rated voltage must be provided. The circuit breaker must meet the following requirements:
- UL Recognized
- CSA Approved (Recommended)
- VDE Approved (Recommended)
- Support the maximum load (20A)
- Support the installation voltage (-40V to -72VDC, as required by the power supply)
- Rated for DC use
A recommended breaker is: Airpax IELK1-1-72-20.0-01-V. The terminal option used will depend on the installation. This breaker is a single pole, 20A breaker with a DC rating of 80V. It is listed as having a long delay. Information about this breaker can be found at http://www.airpax.net/site/utilities/eliterature/pdfs/ial.pdf.
Minimum Wire Size Requirements
Power feeds with three wires (one circuit) per raceway may use 12 AWG wire. Power feeds with more than one circuit per raceway must use 10 AWG wire. Note that the two separate feeds for the redundant supplies are two circuits and must use 10 AWG wire.
Grounding/Earthing Requirements
The Firepower System must be grounded to the Common Bonding Network.
Bonding Locations
Ground bonding locations are provided on the rear of the chassis. M4 studs are provided. Outside-toothed lock washers are provided for attaching ring terminals. A standard ground symbol is available by each stud.
The following illustration indicates the bonding locations on the 1U chassis.
Recommended Terminals
You must use UL-Approved terminals for the ground connection. Ring terminals with a clearance hole for 4mm or #8 studs may be used. For 10-12 AWG wire, Tyco 34853 is recommended. This is a UL-approved, ring terminal with a hole for a #8 stud.
Ground Wire Requirements
The ground wire must be sized sufficiently to handle the current of the circuit in case of a single fault. The size of the ground wire should be equal to the current of the breaker used to protect the circuit. For AC circuits, see AC Current. For DC currents, see DC Current.
Bare conductors must be coated with antioxidant before crimp connections are made. Only copper cables can be used for grounding purposes.
DC Supplies
The DC power supplies have additional ground connections on each supply. This allows the hot-swappable supply to be connected to power, return and ground so that it may be safely inserted. This ground lug must be attached.
It is a M4 screw with an outside-toothed lock washer screw.
The ground wire should be sized to match the breaker for the circuit.
Firepower 82xx Family Appliances
This section describes the power requirements for:
- Firepower 8250, 8260, 8270, and 8290 (CHAS-2U-AC, CHAS-2U-DC, or CHAS-2U-AC/DC)
These appliances are suitable for installation by qualified personnel in network telecommunication facilities and locations where the National Electric Code applies.
Cisco recommends that you save the packing materials in case a return is necessary.
For more information, see the following sections:
- See AC Installation for circuit installation, voltage, current, and frequency range, and power cord information.
- See DC Installation for circuit installation, voltage, current, ground references, terminals, breaker requirements, and minimum wire size.
- See Grounding/Earthing Requirements for bonding locations, recommended terminals, ground wire requirements, and DC supplies.
AC Installation
The Firepower System must be installed in accordance with the requirements of Article 250 of NFPA 70, National Electric Code (NEC) Handbook, and local electrical codes.
Caution
Do
not connect DC power to AC supplies.
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each one must be rated the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different 220V circuit. Each circuit must be capable of supplying 5A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same 220V circuit. The maximum draw from this circuit would be 5A, as stated on the label.
AC Voltage
The power supplies will work with these voltages: 100VAC to 240VAC nominal (85VAC to 264VAC maximum). Use of voltages outside this range may cause damage to the appliance.
AC Current
The labeled current rating for each supply is: 8A maximum over the full range, per supply 4A maximum for 187VAC to 264VAC, per supply. Appropriate wire and breakers must be used to reduce the potential for fire.
Frequency Range
The frequency range of the AC power supply is 47 Hz to 63 Hz. Frequencies outside this range may cause the appliance to not operate or to operate incorrectly.
Power Cords
The power connections on the power supplies are IEC C14 connectors and they will accept IEC C13 connectors. A UL-recognized power cord must be used. The minimum wire gauge is 16 AWG. The cords supplied with the appliances are 16 AWG, UL-recognized cords with NEMA 515P plug. Contact the factory about other power cords.
DC Installation
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Caution
Do
not connect AC power to DC supplies.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each circuit must be rated to the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different –48VDC circuit. Each circuit must be capable of supplying 20A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same –48VDC circuit. The maximum draw from this circuit would be 20A, as stated on the label.
Caution
Use of this optimization requires that the power cords are rated for the full rating for each supply.
DC Voltage
The power supplies will work with these voltages:
- -48VDC nominal referenced to RTN
- -40VDC to -72VDC maximum
Use of voltages outside this range may cause damage to the appliance.
DC Current
18A maximum, per supply
Ground Reference
The DC power supplies are fully isolated from the ground reference.
Recommended Terminals
Power is connected to the DC supplies through screw terminals. Terminals must be UL approved. Terminals must have a hole supporting an M4 or a #8 screw. The maximum width of the terminal is 8.1mm (0.320”). A representative spade terminal for 10-12 gauge wire is Tyco 325197.
Breaker Requirements
A breaker sufficient to carry the rated current at the rated voltage must be provided. The circuit breaker must meet the following requirements:
- UL Recognized
- CSA Approved (Recommended)
- VDE Approved (Recommended)
- Support the maximum load (20A)
- Support the installation voltage (-40V to -72VDC, as required by the power supply)
- Rated for DC use
A recommended breaker is: Airpax IELK1-1-72-20.0-01-V. The terminal option used will depend on the installation. This breaker is a single pole, 20A breaker with a DC rating of 80V. It is listed as having a long delay. Information about this breaker can be found at http://www.airpax.net/site/utilities/eliterature/pdfs/ial.pdf.
Minimum Wire Size Requirements
Power feeds with three wires (one circuit) per raceway may use 12 AWG wire. Power feeds with more than one circuit per raceway must use 10 AWG wire. Note that the two separate feeds for the redundant supplies are two circuits and must use 10 AWG wire.
Grounding/Earthing Requirements
The Firepower System must be grounded to the Common Bonding Network.
Bonding Locations
Ground bonding locations are provided on the rear of the chassis. M4 studs are provided. Outside-toothed lock washers are provided for attaching ring terminals. A standard ground symbol is available by each stud.
The following illustration indicates the bonding locations on the 2U chassis.
Recommended Terminals
You must use UL-Approved terminals for the ground connection. Ring terminals with a clearance hole for 4mm or #8 studs may be used. For 10-12 AWG wire, Tyco 34853 is recommended. This is a UL-approved, ring terminal with a hole for a #8 stud.
Ground Wire Requirements
The ground wire must be sized sufficiently to handle the current of the circuit in case of a single fault. The size of the ground wire should be equal to the current of the breaker used to protect the circuit. For AC circuits, see AC Current. For DC currents, see DC Current.
Bare conductors must be coated with antioxidant before crimp connections are made. Only copper cables can be used for grounding purposes.
DC Supplies
The DC power supplies have additional ground connections on each supply. This allows the hot-swappable supply to be connected to power, return and ground so that it may be safely inserted. This ground lug must be attached.
It is a M4 screw with an outside-toothed lock washer screw.
The ground wire should be sized to match the breaker for the circuit.
Firepower and AMP 83xx Family Appliances
This section describes the power requirements for:
- Firepower and AMP 8350, 8360, 8370, and 8390 (PG35-2U-AC/DC)
These appliances are suitable for installation by qualified personnel in network telecommunication facilities and locations where the National Electric Code applies.
Cisco recommends that you save the packing materials in case a return is necessary.
For more information, see the following sections:
- See AC Installation for circuit installation, voltage, current, and frequency range, and power cord information.
- See DC Installation for circuit installation, voltage, current, ground references, terminals, breaker requirements, and minimum wire size.
- See Grounding/Earthing Requirements for bonding locations, recommended terminals, ground wire requirements, and DC supplies.
AC Installation
The Firepower System must be installed in accordance with the requirements of Article 250 of NFPA 70, National Electric Code (NEC) Handbook, and local electrical codes.
Caution
Do
not connect DC power to AC supplies.
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each one must be rated the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different 220V circuit. Each circuit must be capable of supplying 10A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same 220V circuit. The maximum draw from this circuit would be 10A, as stated on the label.
AC Voltage
The power supplies will work with these voltages: 100VAC to 240VAC nominal (85VAC to 264VAC maximum). Use of voltages outside this range may cause damage to the appliance.
AC Current
The labeled current rating for each supply is: 11A maximum over the full range, per supply 5.5A maximum for 187VAC to 264VAC, per supply. Appropriate wire and breakers must be used to reduce the potential for fire.
Frequency Range
The frequency range of the AC power supply is 47 Hz to 63 Hz. Frequencies outside this range may cause the appliance to not operate or to operate incorrectly.
Power Cords
The power connections on the power supplies are IEC C14 connectors and they will accept IEC C13 connectors. A UL-recognized power cord must be used. The minimum wire gauge is 16 AWG. The cords supplied with the appliances are 16 AWG, UL-recognized cords with NEMA 515P plug. Contact the factory about other power cords.
DC Installation
Separate circuits are required to create redundant power sources. Use an uninterruptible or battery-backed power source to prevent power status issues or power loss due to input line power glitches. The power supplies are hot-swappable.
Caution
Do
not connect AC power to DC supplies.
Supply sufficient power to each power supply to run the entire appliance. The voltage and current ratings for each supply are listed on the label on the appliance.
Use an external Surge Protection Device at the input of the network equipment where the Firepower System is to be installed.
Separate Circuit Installation
If separate circuits are used, each circuit must be rated to the full rating of the appliance. This configuration provides for circuit failure and power supply failure.
Example: Each supply is attached to a different –48VDC circuit. Each circuit must be capable of supplying 25A, as stated on the label.
Same Circuit Installation
If the same circuit is used to feed both supplies, then the power rating of one supply applies to the whole box. This configuration only provides protection from a power supply failure.
Example: Both supplies are attached to the same –48VDC circuit. The maximum draw from this circuit would be 25A, as stated on the label.
Caution
Use of this optimization requires that the power cords are rated for the full rating for each supply.
DC Voltage
The power supplies will work with these voltages:
- -48VDC nominal referenced to RTN
- -40VDC to -72VDC maximum
Use of voltages outside this range may cause damage to the appliance.
DC Current
25A maximum, per supply
Ground Reference
The DC power supplies are fully isolated from the ground reference.
Recommended Terminals
Power is connected to the DC supplies through screw terminals. Terminals must be UL approved. Terminals must have a hole supporting an M4 or a #8 screw. The maximum width of the terminal is 8.1mm (0.320”). A representative spade terminal for 10-12 gauge wire is Tyco 325197.
Breaker Requirements
A breaker sufficient to carry the rated current at the rated voltage must be provided. The circuit breaker must meet the following requirements:
- UL Recognized
- CSA Approved (Recommended)
- VDE Approved (Recommended)
- Support the maximum load (20A)
- Support the installation voltage (-40V to -72VDC, as required by the power supply)
- Rated for DC use
A recommended breaker is: Airpax IELK1-1-72-20.0-01-V. The terminal option used will depend on the installation. This breaker is a single pole, 20A breaker with a DC rating of 80V. It is listed as having a long delay. Information about this breaker can be found at http://www.airpax.net/site/utilities/eliterature/pdfs/ial.pdf.
Minimum Wire Size Requirements
Power feeds with three wires (one circuit) per raceway may use 12 AWG wire. Power feeds with more than one circuit per raceway must use 10 AWG wire. Note that the two separate feeds for the redundant supplies are two circuits and must use 10 AWG wire.
Grounding/Earthing Requirements
The Firepower System must be grounded to the Common Bonding Network.
Bonding Locations
Ground bonding locations are provided on the rear of the chassis. M4 studs are provided. Outside-toothed lock washers are provided for attaching ring terminals. A standard ground symbol is available by each stud.
The following illustration indicates the bonding locations on the 83xx Family 2U chassis.
Recommended Terminals
You must use UL-Approved terminals for the ground connection. Ring terminals with a clearance hole for 4mm or #8 studs may be used. For 10-12 AWG wire, Tyco 34853 is recommended. This is a UL-approved, ring terminal with a hole for a #8 stud.
Ground Wire Requirements
The ground wire must be sized sufficiently to handle the current of the circuit in case of a single fault. The size of the ground wire should be equal to the current of the breaker used to protect the circuit. For AC circuits, see AC Current. For DC currents, see DC Current.
Bare conductors must be coated with antioxidant before crimp connections are made. Only copper cables can be used for grounding purposes.
DC Supplies
The DC power supplies have additional ground connections on each supply. This allows the hot-swappable supply to be connected to power, return and ground so that it may be safely inserted. This ground lug must be attached.
It is a M4 screw with an outside-toothed lock washer screw.
The ground wire should be sized to match the breaker for the circuit.