telecom@eecs.nwu.edu (TELECOM Moderator) (10/12/89)
In the first article in this issue of the Digest, Larry Lippman gives a technical description of Automatic Door Answering Service, or ADAS. In this message, I will describe three installations here in Chicago. Each of the three has certain things in common with the other two, yet each has certain features not found on the other two. First, some definitions: The pre-divestiture ADAS here was marketed by Illinois Bell as 'Enterphone Service'. It was a CO-based offering, with all equipment in the central office except for the relay which allowed the building entrance door to be unlatched. After divestiture, this service could no longer be provided by Illinois Bell; however existing customers were grandfathered; several still remain in operation. The post-divestiture ADAS is marketed by *Illinois Bell Communications*, (a subsidiary of Ameritech, as is Illinois Bell *Telephone Company*) under the name 'Interphone Service'. This is premise-based equipment, and the unit they were selling a couple years ago was manufactured by GTE/Canada. Both systems do essentially the same thing: A panel phone is located near the entrance to the apartment building or small office complex. Vistors use the phone to dial a three digit code number, from a directory of tenants posted there. The three digit code, for security reasons, does not relate to any specific apartment or building location. It is up to the person who answers the call to give you that information. In both instances, the three digits dialed are translated to a specific wire pair (either a dedicated pair from the CO to the apartment, or a house pair to the apartment in the case of Interphone). The device camps-on the pair and first tests for busy. If the line is free, it rings the telephone attached. If the line is busy, it sends a 'call-waiting' tone. The telephone rings in a different way (usually two short rings) to advise the apartment dweller of the nature of the call; allowing it to go unanswered if desired, without fear of missing a 'real' phone call. The apartment occupant answers the phone. In the case of call-waiting, the CO line is put on hold while the door is answered. After conversation with the party at the door, the occupant can choose to admit the visitor or deny entrance. Dialing '4' causes the electric striker on the door to release for a given period, usually five to ten seconds. Dialing '6' denies entrance. If either the occupant or the visitor simply terminates the conversation by replacing the receiver, this is treated as a denial. If a call was on hold, it 'rings back' to remind the person to continue the original call. In either case, the phone line is disconnected, and the occupant is automatically returned to the call in progress if there was one, or is given dial tone. Calls from the front door are limited to a total of sixty seconds, including the time the phone is ringing. Less sophisticated systems use an auto-dialer as part of the premise equipment to dial the directory number of the occupant. A hazard to this approach is that unless the occupant has call-waiting, a visitor at the door would recieve a busy-signal. This style of unit is not used very often these days for this reason, as well as for security problems. The I/Enterphone system does not honor call-forwarding, nor will it send a signal to a physically-bridged off premise extension, such as an answering service. The CO-based system will allow an OPX to manipulate the entranceway, but only if by coincidence the pair from the CO is multipled somewhere in the vicinity of the subscriber's premises and no one bothered to open it up. Both systems are subject to having answering machines accept the call if no one is at home; thus a visitor at the front door can leave a message for the resident if desired. If the occupant for whatever reason does not have telephone service, then an accomodation is made as follows: In the CO-based version, Illinois Bell provides the occupant with a black, rotary-dial phone good for answering the door only. At any other time, the phone is dead. No battery, no sidetone, nothing. It has no directory number -- just a pair assignment. In the premise-based version, the vendor supplies a few phones to the proprietor, or landlord, who is responsible for giving out the phones to new tenants until such time as their regular phone service is connected and they have instruments of their own. If a tenant has more than one phone line, then usually when the ADAS is installed, one line or the other is selected for use with the door. In some cases, the ADAS line is kept on a separate instrument not associated with phone service even if the tenant does have a phone. Illinois Bell *Telephone* leases their CO-based ADAS for about $100 per month. They charge $50 for the common equipment at the CO; $10.75 for the front door phone and CO line; $10.75 for the circuit to the front door and associated relay (which is on premises); plus $1.00 per tenant/ month. Typically, an apartment building with Enterphone has between 30-50 apartments being serviced. Repair of the system with a four hour turnaround, seven days per week, twenty-four hours per day is guaranteed. The landlord of course is responsible for repair of the door and the electric striker, plus the wiring from the premises relay to the door. The building address is flagged in business office records so that any change in service; disconnection of service; installation of new service or whatever MUST take into account the pairs from the CO dedicated to the building. A tenant may be cut due to a credit disconnect, but the Enterphone stays on, since this is billed to the landlord. The pairs can never be assigned to another location, and are tagged this way in the CO. The Illinois Bell Communications premise-based system is offered for sale only. No lease is available, however there are repair packages offered. Like the CO version, once in operation, the incoming pairs from the CO terminating in the building IT, or main terminal are tagged, and installers who come to the building for any reason MUST make sure not to swap out house pairs and CO pairs without keeping things where they belong on the Interphone. One Interphone system here uses a panel speakerphone rather than a regular phone at the front door. It goes 'off hook' when the first digit of three is pressed on the buttons. Another building here uses Interphone also, but that system has both a front and back entrance connected. Tenants dial '4' to open front door, '5' to open back door and '6' to deny entrance at either. In addition, this building has an 'extension' of the front door phone at a desk where the receptionist is seated. The receptionist can call any apartment to announce guests already in the lobby. The receptionist also has a code on the outside phone (dial zero) for someone wishing entrance such as a delivery person. A third building here has Enterphone, but it is hooked up in such a way that the manager and building engineer both have 'extensions' to the front door phone in their apartments, and can call tenants. Interphone can be equipped with a special, secret three digit code which functions like a 'loop around': Dial it, and the system responds by simply unlocking the door. Needless to say for security reasons, this information remains a secret with the building manager or caretaker. Interphone code numbers can be changed easily with simple programming using a phone plugged into the control unit. Enterphone code numbers are a bit more difficult, and require a change order in the business office, with attendant fees for the work, etc, and a lot of beaurocratic hassles. Patrick Townson