Installing an Intercom

• Telephone-based intercoms   Using the existing or standard telephone wiring and standard phones in a home, a doorbell intercom unit, like the one shown in Figure 27-17, can be installed to enable the doorbell unit to ring a unique ring throughout the home on standard telephones and provide intercom service between the door and the telephones.

  
  Figure 27-17: A door intercom that connects into a home’s telephone system

Photo courtesy of LocalPlex.

Chapter Review

The design process for residential telephone systems includes telecommunication wiring schemes, outlet boxes, wire termination, jacks , punchdown blocks, patch panels, wire identification and labeling, and telephone key sets. Telephone wiring is installed using either series wiring or star/home run wiring, but star/home run wiring is preferred.

The telephone wiring inside a home is the responsibility of the homeowner . It is important to use only category verified wiring that meets or exceeds industry, fire, electrical, and materials specifications and standards, and local building codes. Current industry standards specify a minimum of UTP Cat 3 wiring. However, most new construction installs Cat 5e wiring.

There are four basic elements to a home telephone system: structured wiring, outlet jacks, punchdown or distribution blocks, and phone devices. Wiring installed by the telephone company can include 25-pair cable, satin cord , or four-conductor station wire.

Structured wiring support for a telephone system must address standard phone outlet wiring, structured wiring cable, punchdown/distribution blocks, and connections to the demarc.

Modular jacks are common in most existing homes . This type of jack is surface mounted and provides connection for up to two communication lines on a single jack. Flush-mounted wall outlet jacks are more common in newer homes.

A KSU-based telephone system has its own separate controller that provides many of the same Telco subscriber services to the telephones in the home. The features provided by a residential KSU system include the capability to connect to standard telephones, voice-messaging (voicemail), station-to-station intercom support, auto-attendant, music-on-hold , caller ID, and, in many cases, support for a door intercom. A KSU telephone system is preprogrammed with its basic functions. To add additional phones or features, some adjustments may be required to the KSU’s programming. Prior to beginning any programming or station configuration changes, you should summarize the system’s features on a worksheet that documents the number of telephones to be installed and the features available to each telephone. A worksheet should be used to record the KSU system’s features desired by the homeowners.

There are three basic types of intercom systems: independent intercoms, stand-alone, and telephone-based intercoms. The most common types of independent intercoms are: HomePNA intercoms, PLC intercoms, and wireless intercoms. Stand-alone intercoms are self-contained systems that communicate over dedicated wiring. Telephone-based intercoms allow for intercom service between the doorbell and the house telephones.

Questions

1. Under a structured wiring approach, telephone systems should be installed using what wiring scheme?

   1. Series

   2. Bus

   3. Ring

   4. Star

2. What device is placed at the center of the structured wiring for a telephone system?

   1. RJ-11 outlet

   2. Distribution panel

   3. Demarc

   4. Telephone key set

3. Virtually all household wiring standards require the use of what type of wiring?

   1. Cat 3

   2. UL Category verified

   3. Riser

   4. Plenum

4. A type of telephone system that is implemented on a central control unit that supports standard telephones or proprietary phones is a/an:

   1. Intercom

   2. KSU

   3. Telco

   4. Wireless

5. Which of the following is not a type of intercom system?

   1. Stand-alone

   2. Independent

   3. Telephone-based

   4. KSU

6. Which of the following should be done before making any programming changes to a KSU system? (There may be more than one answer.)

   1. Complete features worksheet

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   3. Program telephone

   4. Remove default programming

7. What cable is typically used to connect a telephone key set to a wall outlet?

   1. Station wire

   2. Coaxial cable

   3. Satin cord

   4. Zip wire

8. Which of the following is not a type of outlet jack commonly associated with telephone connections?

   1. F-type

   2. Modular

   3. Face plate

   4. Inline

9. What do the terms Tip and Ring refer to?

   1. Incoming signal and bell

   2. Positive and negative

   3. Ring and busy tones

   4. Dial and busy tones

10. How many phone lines can be supported by a single run of Cat 3 or Cat 5 cable?

    1. Two

    2. Three

    3. Four

    4. Six