Reference Designs
This section offers specific examples of how Littelfuse circuit protection devices can be used to ensure longterm operability of protected equipment and uninterrupted service during overcurrent and transient electrical activity.
For assistance on new designs not covered below, contact a littelfuse technical support for assistance.
For assistance on new designs not covered below, contact a littelfuse technical support for assistance.
Triac Protection
Damage can occur to a thyristor if the thyristor's repetitive peak off-state voltage is
exceeded. A thyristor's repetitive peak off-state voltage may be exceeded due to dirty AC
power mains, inductive spikes, motor latch up, and so on.
Secondary Telecom Protection
Secondary protectors (stand alone units or integrated into strip protectors and UPSs) are
adjunct devices used to enhance the protection level of customer premise equipment
(CPE). Due to the inadequate level of protection designed into CPE, secondary protectors
often are required to prevent premature failure of equipment exposed to environmental
hazards.
Primary Telecom Protection
Primary telecommunications protectors must be deployed at points where exposed twisted
pairs enter an office building or residence. This requirement is mandated in North America
by the National Electric Code (NEC) to protect end users from the hazards associated with
lightning and power cross conditions.
PBX Systems
PBXs, KSUs, and PABXs contain line cards that support various transmission protocols
such as ISDN, T1/E1, HDSL, and ADSL. PBXs also have features such as a POTS (plain old telephone service) pull-through which allows stations to have outside line access in the event of power failure. All incoming lines to the PBX are subject to environmental hazards such as lightning and power cross.
High Speed Transmission Equipment
High speed transmission equipment encompasses a broad range of transmission protocols
such as T1/E1, xDSL, and ISDN. Transmission equipment is located at the central office,
customer premises, and remote locations.
Data Line Protectors
In many office and industrial locations, data lines (such as RS-232 and ethernet) and AC
power lines run in close proximity to each other, which often results in voltage spikes being
induced onto the data line, causing damage to sensitive equipment.
Customer Premises Equipment (CPE)
CPE is defined as any telephone terminal equipment which resides at the customer's site
and is connected to the Public Switched Telephone Network (PSTN). Telephones, modems,
caller ID adjunct boxes, PBXs, and answering machines are all considered CPE.
CATV Equipment Protection
As cable providers enter the local exchange market, protection of CATV (Community
Antenna TV) equipment becomes even more critical in order to ensure reliable operation of
equipment and uninterrupted service.
Analog Line Cards
Given that line cards are highly susceptible to transient voltages, network hazards such as
lightning and power cross conditions pose a serious threat to equipment deployed at the
central office and in remote switching locations. To minimize this threat, adequate levels of
protection must be incorporated to ensure reliable operation and regulatory compliance.
Analog Line Cards
Given that line cards are highly susceptible to transient voltages, network hazards such as
lightning and power cross conditions pose a serious threat to equipment deployed at the
central office and in remote switching locations. To minimize this threat, adequate levels of
protection must be incorporated to ensure reliable operation and regulatory compliance.
CATV Equipment Protection
As cable providers enter the local exchange market, protection of CATV (Community
Antenna TV) equipment becomes even more critical in order to ensure reliable operation of
equipment and uninterrupted service.
Customer Premises Equipment (CPE)
CPE is defined as any telephone terminal equipment which resides at the customer's site
and is connected to the Public Switched Telephone Network (PSTN). Telephones, modems,
caller ID adjunct boxes, PBXs, and answering machines are all considered CPE.
Data Line Protectors
In many office and industrial locations, data lines (such as RS-232 and ethernet) and AC
power lines run in close proximity to each other, which often results in voltage spikes being
induced onto the data line, causing damage to sensitive equipment.
High Speed Transmission Equipment
High speed transmission equipment encompasses a broad range of transmission protocols
such as T1/E1, xDSL, and ISDN. Transmission equipment is located at the central office,
customer premises, and remote locations.
PBX Systems
PBXs, KSUs, and PABXs contain line cards that support various transmission protocols
such as ISDN, T1/E1, HDSL, and ADSL. PBXs also have features such as a POTS (plain old telephone service) pull-through which allows stations to have outside line access in the event of power failure. All incoming lines to the PBX are subject to environmental hazards such as lightning and power cross.
Primary Telecom Protection
Primary telecommunications protectors must be deployed at points where exposed twisted
pairs enter an office building or residence. This requirement is mandated in North America
by the National Electric Code (NEC) to protect end users from the hazards associated with
lightning and power cross conditions.
Secondary Telecom Protection
Secondary protectors (stand alone units or integrated into strip protectors and UPSs) are
adjunct devices used to enhance the protection level of customer premise equipment
(CPE). Due to the inadequate level of protection designed into CPE, secondary protectors
often are required to prevent premature failure of equipment exposed to environmental
hazards.
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