TelecomMultiUnit Telecommunication lines are very often the overlooked "back door" for transients to enter your facility.  Telecommunication equipment often suffers the highest rate of catastrophic damage to any system within a facility.  Protecting incoming telecommunications lines and lines running from one building to another is not only prudent, it is an  NEC requirement.  

  • POTS, ISDNDSL, T1, Fax and Modem Lines
  • Terminal Strip, Modular Jack and Punch-down Block Configurations
  • Lowest Let-through Voltage Levels
  • UL497A


   Telecom Data Sheets

Telecom surge protective devices are utilized to protect incoming telephone lines. They are also used to protect internal station lines running between buildings on the same system. There are a variety of “phone” lines. These include the Plain Old Telephone Service (POTS) line, Integrated Services Digital Network (ISDN) line, Digital Subscriber Line (DSL), T-1 line and T-3 line. The small size and variety of connection options make the telecom SPDs an easy solution for achieving protection across all of the line types.


The Plain Old Telephone Service (POTS) line is a standard, voice-grade telephone line with a dial tone. It is a two wire (tip & ring) circuit. Tip and Ring are telephony slang for the two wires which make up the electrical circuit used for telephone wiring. Tip is the nickname for the electrically positive wire and Ring is the nickname for the electrically negative wire. Tip is the ground side, which is positively charged, and Ring is the battery side, which is negatively charged, of a telephone circuit. The tip is synchronized with the office of the telephone company.


Integrated Services for Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the traditional circuits of the public switched telephone network. It was first defined in 1988 in the CCITT red book. Prior to ISDN, the telephone system was viewed as a way to transport voice, with some special services available for data. The key feature of ISDN is that it integrates speech and data on the same lines, adding features that were not available in the classic telephone system. There are several kinds of access interfaces to ISDN defined as Basic Rae Interface (BRI), Primary Rate Interface (PRI), Narrowband ISDN (N-ISDN), and Broadband ISDN(B-ISDN).


Digital subscriber line (DSL; originally digital subscriber loop) is a family of technologies that are used to transmit digital data over telephone lines. In telecommunications marketing, the term DSL is widely understood to mean asymmetric digital subscriber line (ADSL), the most commonly installed DSL technology, for internet access. DSL service can be delivered simultaneously with wired telephone service on the same telephone line. This is possible because DSL uses higher frequency bands for data. On the customer premises, a DSL filter on each non-DSL outlet blocks any high-frequency interference to enable simultaneous use of the voice and DSL services.


T-1 is a hardware specification for telecommunications trunking. A trunk is a single transmission channel between two points on the network: each point is either a switching center or a node (such as a telephone). T-1 lines are a method of combining multiple telephone lines onto a single line consisting of one, or two pairs of wires. A T-1 line typically has 24 telephone lines available at the same time.

T-2 & T-3:

The T2 and T3 circuit channels carry multiple T1 channels multiplexed, resulting in transmission rates of 6.312 and 44.736 Mbit/s, respectively. A T3 line comprises 28 T1 lines, each operating at a total signaling rate of 1.544 Mbit/s. It is possible to get a fractional T3 line, meaning a T3 line with some of the 28 lines turned off, resulting in a slower transfer rate but typically at reduced cost.