The invention relates to electronic entry control systems, and more particularly to self-contained electronic directory and entry control systems having liquid crystal directory displays, used to control access to apartment buildings and the like.
In apartment buildings, commercial office buildings, and other multi-tenant complexes, it is common practice to limit access to common areas to those individuals living and/or working within the complex, as well as their authorized guests and visitors. Of course, this can be accomplished in a simplistic manner by merely locking all access doors and providing tenants with keys. However, this approach has proven to be inconvenient and cumbersome in the admission of guests and visitors, as the tenant must physically unlock the door each time someone is to be admitted. Furthermore, with such a system, it is often difficult to determine whether a person is present at a door and desires admission. In the business environment, this can lead to a substantial loss in productivity.
One past attempt to resolve this problem has focused on the use of a dedicated intercom system. In such a system, a visitor actuates a button on an intercom panel outside the complex, alerting the desired tenant to his presence. Optionally, voice communication capability can be provided so that the visitor can establish his identity. Once it has been determined that the visitor is authorized to be admitted, the tenant can either physically unlock the door himself or press a button on the interior intercom panel to actuate a door unlocking mechanism.
The intercom system has several disadvantages. First, significant dedicated wiring is required to support the intercom at the entry door and to provide communication with each tenant unit. Furthermore, if remote door actuation capability is to be provided, further rewiring can be necessary. Expensive intercom hardware is required to be installed within each tenant unit. Finally, if many tenants reside within the complex, providing an individual "call" button for each tenant can result in a prohibitively large intercom unit at the entry door.
In response to the disadvantages of entry systems using dedicated intercoms, telephone-based entry systems have been proposed. Significant rewiring is not necessary, other than to provide electrical power and telephone line access to the station at the entry door. When a visitor desires access, he will place a telephone call from the entry system to the desired tenant, who will either physically unlock the door or, by using the touch-tone keypad on the telephone, provide an authorization signal to the entry system, which will then actuate a door unlocking mechanism. Additional expensive hardware is not needed for each tenant unit, as substantially all tenants have access to telephone equipment and a telephone line. Finally, since each tenant is addressable through a unique telephone number, a separate call button for each tenant is not necessary; numeric codes can be used.
With the resolution of the foregoing recognized problems by the use of telephone-based entry systems, other disadvantages have become apparent. Where a typical intercom system might have a separate call button for each individual tenant, each button can be labeled, making it easy to locate any desired tenant. Where no individual call buttons exist, however, a separate directory of tenants should be provided. Where there is a large number of tenants, the directory can be physically quite large. Moreover, labor involved in the maintenance of such directories to reflect tenant turnover can be significant, particularly when there are several entry doors to the complex.
Accordingly, the need for an easily updatable electronic directory has been recognized. Such a goal is readily accomplished by using digital computer technology. As is well known, a small digital computer, with memory, can be used to store tenant names, telephone numbers, access codes, dialing codes, and other information within the entry system, at the expense of little additional cost or size. The electronic storage of such information makes it possible to update directory information with little or no effort; the revised information can be communicated to the digital computer through a data port, or even remotely via telephone lines.
The use of an electronic display, however, introduces further difficulties. Various display technologies are known and available for use. For example, a cathode ray tube ("CRT") video display, as is typically used for desktop computers, can easily be adapted for use as a directory display. However, CRT displays are generally large, heavy, and fragile, making them ill-suited for in-wall directory use. Furthermore, CRT displays consume a large amount of power. Light emitting diode ("LED") displays are also known, but are expensive and bulky when produced in sizes sufficient to display directory information. Fluorescent and gas-discharge displays, since they make use of a gas-filled glass tube, are also relatively fragile. Moreover, all of the foregoing display devices are light-emitting, which makes them difficult to see under bright light conditions, as in direct sunlight.
Liquid crystal displays ("LCDs") are also known. They have the advantages of low cost and low power requirements. Such displays are selectively reflecting rather than light-emitting, so they are best viewed with ambient light, including bright light conditions that would "wash out" other types of displays. However, LCDs are also easily viewable in low light conditions when backlit.
Unfortunately, LCDs are known to be temperature-sensitive. As temperature increases, the contrast of the display will often decline until it is unreadable. This is a particular problem where entry systems utilizing LCD directories are installed outdoors, in direct sunlight, or elsewhere under adverse temperature conditions. Furthermore, when an LCD is installed in a sealed enclosure with a viewing window, the temperature inside the enclosure may increase to a level far beyond the air temperature outside the enclosure due to a "greenhouse effect."
A variety of attempts have been made to solve the temperature sensitivity problem; none has proven to be entirely successful. One possibility is to provide a "hood" over the display to ensure that the display is shaded. This approach has the disadvantage of reducing the amount of light reaching the display, and it also limits the angles from which the display may be viewed. Furthermore, such an approach does not provide temperature reduction, per se; it merely reduces the possibility that direct sunlight from certain angles will raise the temperature.
A second possibility is to ventilate the enclosure containing the LCD. However, this raises an opportunity for potential vandalism and damage to the entry system, as access to the interior of the enclosure is provided. Furthermore, ventilation of air to the interior of the enclosure will also allow the elements to invade the enclosure to some extent. Damage from oxidation, moisture, and other contaminants can accelerate the deterioration of the entry system and impair reliability. A further possibility is to provide a cooling fan. This, too, is unsatisfactory: moving parts are added to a system that could otherwise be entirely without them; furthermore, mechanical fans are noisy and potentially unreliable. When a fan is provided within a sealed enclosure, very little cooling action is possible.
It is recognized herein that the addition of an electronic display to an entry system complicates the system significantly. Adding the display unit will increase the size and cost of the entry system. Furthermore, if the display unit is of a size insufficient to display all tenant names at one time, a mechanism must be provided to determine which names are shown on the display. This can be accomplished by providing control buttons on the entry system, beyond those necessary for a simple telephonic keypad. Adding these additional controls will further raise the cost and complexity of the system, as well as the operational complexity to a typical user.
Substantially all practical systems of the type described herein providing communications capability between a visitor and a tenant, do so with audio communication. This type of communication is easily accomplished over the telephone system, and requires little additional circuitry or complexity to the system, beyond that already required to access the telephone system. Individuals who are deaf or hearing-impaired are not generally able to use these types of entry systems effectively.
Accordingly, a need exists for an entry control system that avoids the many shortcomings of prior devices. Specifically, a need exists for a self-contained entry system that has a directory display that is easily visible under substantially all lighting conditions, and is resistant to adverse temperature conditions. A further need exists for an entry system that provides accessibility to deaf and hearing-impaired individuals. To reduce costs, such a system should minimize unneeded complexity.