Home > Articles > Networking > Voice/IP Communications

This chapter is from the book

Creating an Intercom

Cisco CME supports single-button push-to-talk and push-to-respond intercom lines. You can create an intercom arrangement between any two (multiline) IP phones that support speakerphone operation. You can even operate an intercom across a VoIP connection using either SIP or H.323. Cisco CME's intercom function is built using two functions:

  • Autodial at the initiating end of the intercom
  • Autoanswer-with-mute at the receiving end

To create an intercom you assign a line button on each of the two phones to operate as an intercom line. Pressing the intercom line button selects the line and triggers the autodial function toward the second phone. The receiving phone receives the incoming intercom call on its intercom line. This line autoanswers the call and activates the phone in speakerphone mode and sounds a beep. It also forces the speakerphone to mute to protect the privacy of the intercom recipient. The audio path is open from the initiator to the receiver. To respond to the intercom, the recipient simply presses the mute button to unmute the audio path back to the originator.

The intercom Command

Example 5-21 shows a configuration of an intercom between two IP phones.

Example 5-21 Intercom Lines

router#show running-config
ephone-dn 1 dual-line
 number 1001
 name John Smith
ephone-dn 2 dual-line
 number 1002
 name Jane Smith
ephone-dn 3
 number 1111
 intercom 1112 label Jane
ephone-dn 4
 number 1112
 intercom 1111 label John
ephone 12
 mac-address 000d.1234.0efc
 button 1:1 2:3
ephone 15
 mac-address 000d.5678.0dcf
 button 1:2 2:4

Example 5-21 shows two phones. John's phone has button 1 as his primary extension line. Button 2 on John's phone is an intercom line. This line is set to autodial Jane's phone using the number 1111. The button is labeled "Jane" to show that pressing the button intercoms to Jane.

Jane's phone is configured to match to John's phone. Button 1 on Jane's phone is her primary line. Button 2 is set to autodial John's phone and shows the label "John" next to the button. The default configuration for an intercom line is that it autoanswers with mute for any incoming call. Autoanswer can be disabled if desired using the no-auto-answer command option.

Example 5-21 shows a fully symmetric two-way intercom arrangement. John can intercom to Jane, and Jane can intercom to John.

Individual phones may have more than one intercom. The maximum number of intercoms per phone is limited only by the number of available buttons. In general, using intercoms on single-line phones such as the Cisco 7910, 7905, and 7912 is not recommended. These phones do not have a built-in (hands-free) microphone and, therefore, cannot be unmuted without lifting the phone's handset.

Many-to-One Intercom

In the previous example you saw that an intercom line autoanswers any incoming call. The incoming intercom does not perform any type of cross-check on the calling party to ensure that it matches the outgoing intercom destination. This arrangement lets you create a many-to-one intercom, which is useful when you have a single shared assistant working for multiple executives, as shown in Example 5-22.

Example 5-22 Shared-Line Intercom

router#show running-config
ephone-dn 1 dual-line
 number 2101
 name Executive1
ephone-dn 2 dual-line
 number 2102
 name Executive2
ephone-dn 3 dual-line
 number 2103
 name Executive3
ephone-dn 4 dual-line
 number 2201
 name Assistant
ephone-dn 5
 number 1110
 intercom 1110 label Intercom
ephone-dn 6
 number 1111
 intercom 1110 label Intercom
ephone-dn 7
 number 1112
 intercom 1110 label Intercom
ephone-dn 8
 number 1113
 intercom 1110 label Intercom
ephone 12
 mac-address 000d.1234.0efc
 button 1:1 2:6
ephone 13
 mac-address 000d.5678.0dcf
 button 1:2 2:7
ephone 14
 mac-address 000d.4321.0ef7
 button 1:3 2:8
ephone 15
 mac-address 000d.4132.f7e4
 button 1:4 2:5

In Example 5-22, ephones 12 to 14 belong to the three executives 2101 to 2103. The fourth phone, ephone 15, belongs to the assistant. Each of the four phones has its primary line associated with button 1. The second buttons on the three executive phones are configured to intercom to the assistant's intercom line. This configuration provides a many-to-one intercom. Any of the executives can press the button 2 intercom on his or her phone to talk to the assistant. Of course, only one intercom conversation can exist at one time.

Note that the assistant's intercom (ephone-dn 5) is set to autodial itself. It is not possible to create a one-to-many intercom path. The assistant's phone could also be configured to autodial one of the executives.

One-Way Intercoms

In the previous many-to-one intercom example, you saw that the assistant's intercom is configured as a one-way or receive-only intercom. This is done by configuring the intercom line to autodial itself. When the assistant presses the intercom button, he or she hears busy tone.

You can use this technique to configure a one-way intercom even in a simple one-to-one intercom arrangement. A better configuration for a one-way, one-to-one intercom is to use the noautoanswer command option, as shown in Example 5-23.

Example 5-23 One-to-One Intercom

router#show running-config
ephone-dn 1 dual-line
 number 2101
 name Executive
ephone-dn 4 dual-line
 number 2201
 name Assistant
ephone-dn 5
 number 1110
 intercom 1111 label Intercom
ephone-dn 6
 number 1111
 intercom 1110 label Intercom no-auto-answer
ephone 12
 mac-address 000d.1234.0efc
 button 1:1 2:6
ephone 15
 mac-address 000d.4132.f7e4
 button 1:4 2:5

With this arrangement, you still have a direct one-to-one dedicated line between the executive and the assistant. Only the assistant's phone autoanswers incoming calls presented to its intercom line. If the assistant presses the intercom line, the phone still autodials the executive's intercom line. The executive's phone simply rings as for a normal call.

Dialable and Private Intercoms

All the previous intercom examples in this chapter show intercoms configured with ordinary extension numbers. This means that you can dial into the intercom lines from any phone, not just the phones configured for intercom. You can even put the intercom numbers into the Cisco CME system directory or speed-dial lists.

You can make the intercom more restrictive by using the extended DTMF digits A–D as part of the intercom phone number. Because IP phones do not have the A–D DTMF digit keys available on their keypads, if the phone number includes A–D digits, it cannot be dialed from an ordinary phone.

Example 5-24 shows how to restrict intercom numbers so that they cannot be dialed from an ordinary telephone.

Example 5-24 Nondialable Intercom

router#show running-config
ephone-dn 1 dual-line
 number 2101
 name Executive
ephone-dn 4 dual-line
 number 2201
 name Assistant
ephone-dn 5
 number A110
 intercom A111 label Intercom
ephone-dn 6
 number A111
 intercom A110 label Intercom
ephone 12
 mac-address 000d.1234.0efc
 button 1:1 2:6
ephone 15
 mac-address 000d.4132.f7e4
 button 1:4 2:5

In this example, you see that the intercom numbers are set to A110 and A111 using the DTMF A digit as the first digit. This technique is also useful if you are using a dial plan that has only two- or three-digit phone numbers. Use of the extra A–D digits for intercom can free up space in the normal number range for use on regular extension numbers.

Courtesy Phone

A courtesy phone is a phone in a publicly accessible area. The phone is allowed to make calls only to internal numbers, such as calls from a lobby, to request assistance. The phone is not allowed to make calls directly to other extensions or to make external calls.

You can create a courtesy phone using the Cisco CME intercom feature. If you configure a multiline phone with normal extensions and intercom extensions, the phone automatically selects the first available normal extension when you lift the phone handset. The phone never auto selects the intercom line, even if all available normal extension lines are in use (for example, by shared phones).

You can configure an IP phone with only a single line where that single line is an intercom. In this case, when you lift the handset off-hook, the only possible line selection is the intercom line. This line is selected, and the phone autodials to the configured intercom destination. You can use this configuration technique to create a courtesy phone that always dials a fixed destination when the phone is taken off-hook.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020