TSP/ESP Series Secondary  Surge Protectors for Communication Circuits (UL 497A)


Secondary protectors, by definition, are located electrically behind primary protectors on incoming CO trunk lines connected to the telephone network, or on exposed (to power cross) telephone extension tines per NEC article 800.30.

To properly meet code requirements, as well as product longevity expectations, secondary protector installations must have primary protectors installed electrically between them and the outside plant facilities. The secondary protectors are designed to coordinate with the primary protectors in both the surge-handling capabilities, and also in steady excess currents (such as during power cross). Grounding of both the primary and secondary protectors should ultimately be bonded to building approved ground.



Low Voltage Units

The ESP Series protectors are available in several standard low voltage ratings, To properly select an ESP for a given application, one must FIRST know the maximum peak operational voltage on the pairs to be protected. Next, ADD four volts to that number and then SELECT the ESP with a voltage suffix equal to or higher than the calculated number.

An example: We determine that the maximum peak operational voltage is 24 volts. Then, adding four to that number yields a selection voltage minimum of 28 volts. The proper ESP would be an ESP-030.


Ring Voltage Units

EXTENSION circuits when ringing voltage can be present on the 1ine.

The TSP Series protectors are available in a voltage rating suitable for CO TRUNK circuits with presence of
ringing voltage.


For Effective Protection*

1. Protectors must be keyed properly on the 66 block. This is accomplished during initial installation by placing the grounding bar (MGB) on the OUTSIDE PLANT (unprotected) side of the 66 block.

2. A local (at protected equipment) single point ground must be established. This is illustrated later in detail.

*Protectors are installed in place of bridging c]ips on a standard split 66M1-50 block. One ground rail (MGB) is required for each 66 block. This product is for indoor use only.

*Never install telephone wiring during a lightning storm.

*Before installation or servicing, disconnect equipment from network interface to avoid shock hazard.


1. Position the MGB parallel to the outside plant side of the M block.

2. Insert end hook around outside fanning strip of M block and gently pull into place, aligning angle brace as shown in Figure 1.

3. Using mounting hardware provided, attach other end of MGB to M block mounting tab.

4. Tighten mounting screw once MGB is aligned parallel to M block.

5. Connect ground wire to ground lug. Use at least a # 10 gauge wire.

Bond protection ground according to recognized procedures.

6. Simply plug in the TSP/ESP module on M block and MGB. The module replaces the T & R bridging clips. It is suggested to line up the gmund rail connector clip first.

National Electrical Code Wording


(a) Application. A listed protector shall be provided on each circuit run partly or entirely in aerial wire or aerial cable not confined within a block. Also a listed protector shall be provided on each circuit, aerial or underground, so located within the block containing the building served as to be exposed to accidental contact with electric light or power conductors operating at over 300 volts to ground. Installation of protectors shall also comply with Section 110-3(b).

(FPN No. 1); The word "block" as used in this article means a square or portion of a city, town, or village enclosed by streets and including alleys so enclosed but not any street.

(FPN No, 2): The word "exposed" as used in this article means that the circuit is in such a position that, in case of failure of supports or insulation, contact with another circuit may result.

(FPN No.3); On a circuit not exposed to accidental contact with power conductors, providing a listed protector in accordance with this article will help protect against other hazards such as lightning and above-normal voltages induced by fault currents on power circuits in proximity to the communications circuit. When protecting a circuit run within the block between two buildings on the same premises, providing a listed protector on each end of the circuit affords protection for both buildings.


The TSP/ESP Series secondary protectors can be installed as shown in Figures 2 and 3, and be compliant with UL 497A. Article 800.30 of the NEC is reprinted here for your convenience in determining if secondary protection is required as opposed to isolated loop circuit protection UL 497B. Please note that primary protection should always be used in conjunction with secondary protection.

This description fits the vast majority of telephone extension lines that run from building A to building B. Reference Figures 2 and3.


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