Security Communications: Practical Intercom Applications

Dec. 2, 2011
One-on-one authentication by means of verbal communication and often visual confirmation are the basis of high end security management.

Intercom technology used in security continues to evolve as more of these systems come into use and users demand systems which better meet their requirements. In security intercoms provide audible and often visual communications between entry points and occupants or security personal. There are many types of intercoms, and new technologies continue to widen the choices.

Many readers will relate to the traditional apartment lobby panels which were and are widely used in multiple occupancy buildings. These featured lists of tenants and a call button for each tenant. Each tenant had a wall unit which was directly connected to the lobby panel.

When a visitor pressed the tenant’s button, an alert sounded in the apartment, and the tenant responded by talking to the individual in the lobby and granting access by energizing the electric door strike on the building entry door.

Typical failure modes for this type of system include failure of the electric strike, so the door would be propped open until it could be serviced. Also communications between the lobby and apartments might be interrupted by a damaged wire or damaged equipment. On some systems, if a button on an apartment unit stuck, it disabled all the other apartments as well. This resulted in the common practice of an occupant simply granting access without verifying who was coming into the building. This led to the practice of individuals simply pressing all the buttons on the panel and waiting for someone upstairs to admit them so the alert tone would stop.

Although the recurrent service calls for these systems payed many salaries, we nevertheless learned the shortcomings of solid conductor multi-conductor cable, cheap switches and flimsy electric strikes.

Telephone entry systems represented an improvement over the traditional lobby panel by eliminating the need to install wiring between each apartment. The tenants used their telephones, and the lobby unit connected to dial tone. The lobby panels use scrolling displays, and a limited number of buttons or typical telephone-style keypad.

For residential applications, a door station product was introduced which was perfect for door control applications. When the outside button was pressed, every phone on the dialed number had the ability to speak with the door and grant access. The number programmed in could also be offsite.

One of the sources for intercom products I use is a company called Viking Electronics. Viking is a mainstay in the telecom industry, with more than 250 products designed for public address, multi line commercial, emergency communications and access control. This is a “Made in the USA” type company which specializes in quality product and technical support.

They have an exhaustive website,, and also mail out a monthly newsletter. The newsletter reports on new products current events and usually highlights an application based around Viking products.

Q & A: Viking Applications

Recently they had an application where a lobby phone doubled as an access control keypad, which also provides voice communication and remote door control.

We interviewed the author of “Al’s Applications” about Viking and its products. Following are the Ledger’s questions and Al Adams’ answers.

What is your name and job title?

Al Adams, Product Support Supervisor, Viking Technical Support Group, Phone: (715) 386-8666. Fax: (715) 386-4344.

Can you provide some background on Viking?

Viking Electronics, Inc. is a manufacturer of innovative and reliable telecommunication and security products. All Viking products are “Made in the USA” and include ADA compliant emergency phones, door and video entry, paging, mass notification and more. If you should need product support you will be talking to a Viking employee right here in our Hudson, Wisc. plant.  We have 40 years of experience, over 250 products, and thousands of security and communication solutions.

Your article indicates one version of the system uses software. Is the software used only for programming, and how does the computer on which the software is installed communicate with the Viking controller?

The “software” that the application refers to is special controlling software that is installed inside the K-1900-3 or C-4000 controller to change its operation from an apartment entry system to a visitor entry system with keyless entry (for authorized personnel) that is more often used in commercial applications.

With their standard software installed, the K-1900-3 or C-4000 are designed to “speed dial” the phone lines or cell numbers of the tenants in an apartment building, as well as providing a keyless entry code for each tenant to let himself or herself in.

A visitor at the apartment building is provided with simulated dial tone and they must then dial “0” to “250” to call through to one of the apartments in the building.  The person that answers in the apartment can then dial a touch tone command to let them in.  The tenants can dial “#” plus their keyless entry code to let themselves in at the entry phone.

Once the K193F-DEA or C4K-DEA software is installed in the controller, the visitors are no longer forced to dial the “0” to “250” to call through to someone inside (this is a plus as no instructions have to be placed next to the entry phone).  Six seconds of simulated dial tone is provided to allow authorized users to dial “#” plus a valid keyless entry code to let themselves in.  After the six seconds of simulated dial tone (and the visitor has not dialed any digits), the controller automatically speed dials the phone number (or extension number) programmed in the “0” speed dial location.  Their call then goes to an operator or security personnel who then determine if they should be granted access.

In the case of the C-4000, the “C4K-DEA” software is installed by doing a “chip swap” inside the C-4000 (and thus can be done in the field), so the “C4K-DEA” can be purchased separately and installed in a given C-4000 by an installer.  The K-1900-3 does not have this capability of “swapping” chips in the field, so the “K193F-DEA”” software must be installed here at the factory.

Customers normally order the K-1900-3 and the K193F-DEA through their Viking distributor and we install (and test) the special software here at the factory, for a minimal “programming” fee.

What is the interface between the controller and a printer/ computer? Does the system provide real time event log?

Both controllers have a “log bus” output that provides data about each entry that occurs.  The output for this “log bus” data is two screw terminals.  It is up to the installer to connect these two screw terminals to a 9 pin connector so it can be connected to a PC or serial printer (see the attached page 5 of C-4000 instructions).  If connected to a serial printer, the entry data will not be time or date stamped (the controllers do not have internal clocks).  If connected to a PC and they install our “Entry Logger” PC software (free download from our website), the Entry Logger software will time and date stamp each entry, based on the PC date and time.

The C-4000 has a 9 pin jack that is an optional way to program the C-4000’s telephone numbers and keyless entry codes via PC.  The K-1900-3 can only be programmed using a touch tone phone.  The C-4000 can be programmed using a touch tone phone or a PC.  When programming by PC, a visual basic software program must be installed on the PC first (another free download from our website).

Does the system support a door position sensor and forced door alarms or propped door alarms?

No, neither of these controllers have a door sensor input.  I am familiar with this capability as we have a different controller that does have a door sensor input.

If a PIN is not entered within 6 seconds, the controller places a call. Can more than a single number be programmed so if the first number fails to answer, it rolls over? 

No, it can only be programmed to dial one number after the six seconds of simulated dial tone has expired.  If someone needed to dial more than one number (in case of busy or no answer), we could use the K-1900-3 or C-4000 along with one of our “smart” dialers (model K-1900-30).

Once the call is placed, what happens? Can the person called remotely unlock the door?

Yes, once a visitor has called through to the “inside” person, the person inside can dial a one- or two-digit touch tone command to let the visitor in (and the command is programmable).

What are the other functional differences between the two controllers?

Both controllers operate in the same fashion with the main difference being in the number of entry points.  The K-1900-3 can only support one entry phone and the C-4000 supports up to four entry points and provides a separate door strike relay for each entry.  As mentioned earlier, the C-4000 also has an option for PC programming versus touch tone programming (K-1900-3 must be touch tone programmed).  The C-4000 can also support a card reader at each entry point for apartment building applications but card readers would not normally apply to this application.