Door entry control and entrance intercom systems presently available in the market can be classified into three distinct categories: stand-alone intercom systems, systems using automatic ialers and telephone company facilities and the ENTERPHONE system. The following paragraphs describe briefly, each of these types of systems and identify some of the problems encountered with each.

STAND-ALONE INTERCOM SYSTEMS

These systems are used in many existing buildings and provide a two-way intercom path from the lobby or entrance area to each individual suite. A separate speaker and control panel is provided in each suite to allow residents to receive intercom calls from visitors in the lobby area and activate a door-opening mechanism. Some of the shortcomings associated with this type of system are as follows.

I Separate wiring is required from the entrance panel to individual suites. This could involve separate conduits to each suite in addition to the wiring required. This also causes considerable expense and difficulty if owners or residents wish to install a system in an existing building where this wiring has not been provided.

II Generally, one speaker and control panel is provided for each suite. If a resident is outside hearing range of the unit, incoming calls may be missed. Additionally, the resident must leave whatever area he or she is in when the call is heard in order to access the speaker and the control panel.

III The sound reproduction quality of the intercom circuit is generally inferior to the quality of a telephone transmission, and deteriorates with the age of the system.

AUTOMATIC DIALER SYSTEMS

Systems using an automatic dialer represent some improvement over the stand-alone intercom systems, in that they utilize telephone company facilities instead of separate cabling to link the lobby to each suite. When visitors dial the listed suite identification number contained in the lobby directory, the system automatically converts this number to the resident's telephone number and uses an automatic dialer to place the call. The resident receives the call on his or her telephone set and activates the door-opening mechanism by dialing a special code. Some of the difficulties associated with systems of this type are as follows:

I The system requires a separate telephone line to connect to the automatic dialer. This line must be rented from the telephone company on a monthly basis, and is generally paid for by the building owners or the property management company responsible for the building operation.

II If the resident is using the telephone for an outside call, the system will return a busy signal to the lobby visitor. If the resident is not expecting visitors, the outside call could go on for some time while the lobby visitor receives a busy indication.

III If the resident's telephone service or the line connected to the outside dialer is out of order or the telephone company is experiencing trouble within the local switching centre, the intercom/door entry system will not function.

IV Depending upon the length of the cable loop from the building to the telephone company switching centre and back to the resident, the sensitivity of the circuit may not be sufficient to allow the resident to activate the door opening mechanism.

V Should the resident not have service from the telephone company for whatever reason, they cannot be called and therefore, cannot be notified of visitors or control the door.

VI At the present time, the telephone company in Ontario and Quebec is contemplating applying to the C.R.T.C. (Canadian Radio & Telecommunications Commission) for permission to implement a billing procedure whereby users are billed on a per call basis. This billing procedure could dramatically increase the cost of the line used by the auto-dialer.

THE ENTERPHONE DOOR ENTRY SYSTEM

This system uses a unique system architecture to interface directly with the resident's existing telephone without requiring access to outside telephone company facilities. Because of this design, the ENTERPHONE is able to overcome all of the difficulties associated with both the stand-alone intercom systems and those which use the automatic dialer and telephone company facilities. It also provides several features which result in increased convenience and security for the building residents.

No outside telephone company cable or switching facilities are used to complete the circuit, and only a one-time installation charge and no monthly charge is paid to the telephone company by the owners or property manager.

I Calls originating from a lobby or entrance ENTERPHONE panel use the inside building telephone cable and existing resident telephone sets to communicate with each suite. Separate wiring is not required, and systems may be easily installed in existing buildings without expensive restorations.

II No outside telephone company cable or switching facilities are used to complete the circuit, and no monthly line charges are paid to the telephone company by the owners or property managers.

III Incoming calls from the lobby or entrance panel area ring in each suite with a distinctive ringing cycle so that each resident can immediately distinguish between an incoming ENTERPHONE call and a regular telephone call.

IV Lobby calls may be answered from any telephone in the suite, and the door opening mechanism may be activated from any extension.

V Because the ENTERPHONE is a self contained communications system, a telephone set may be installed in the suite separate from the telephone system to permit communication with the lobby and facilitate door control.

VI If a resident is already using the telephone and a visitor activates the ENTERPHONE system, the resident receives a distinct overtone on the line. The resident is then able to place the existing outside call on hold, communicate with the visitor, permit or deny access to the building, and then return to the original conversation. Similarly, if a resident is conversing with a visitor in the lobby using the ENTERPHONE system and an incoming call from outside arrives, the resident is signalled, with a unique overtone on the line. Upon completing the lobby call, the outside call is automatically connected.
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VII Because all of the circuitry of the ENTERPHONE system is contained within the building, problems on the telephone company equipment or on the resident's external telephone line do not affect the operation of the ENTERPHONE. If a particular resident does not wish to have telephone company service, he or she may still receive ENTERPHONE service from a telephone supplied by the building management or purchased directly by the resident.