DERIVED CHANNEL MULTIPLEX - Component Information
The DERIVED CHANNEL MULTIPLEX Network consists of three principal elements;
- CUSTOMER PREMISE EQUIPMENT -
Customer premise equipment consists primarily of the Subscriber Terminal Unit (STUģ), which is located at the customerís home or office, and is connected as a non-ringing extension to the existing telephone line. Itís primary function is to interface the alarm panel (or other signaling devices) to the telephone line and therefore, to the DERIVED CHANNEL MULTIPLEX Network. The STU is designed to interface to a variety of commercially available alarm panels and sensors.
Signals originate from alarm sensors at the premises and enter the network through the STU. Each STU can monitor multiple discreet alarm input zones or communicate with the panel via a serial port, in addition to monitoring supervisory inputs such as low battery, AC Fail, or tamper. The STU connects directly to the customer's telephone line via a standard RJ11 jack, but its use does not preclude the use of the phone by the customer.
- MESSAGE ROUTING EQUIPMENT -
The message routing equipment consists of three main elements; the Scanner, the RScanner, and the Message Switch. Once a message is generated by the STU, it must be sent to the proper monitoring station facility. This is accomplished by the message routing equipment which is installed in the telephone companyís central offices.
The Scanner, which resides at a local telco central office, communicates with the STU (a maximum of 1,024 per Scanner). The Scanner periodically interrogates the STU for messages. Should any STU have an alarm signal to report, it is passed to the Scanner which duplicates the message and passes the duplicate to a redundant part of the Scanner. This pair of messages now travel throughout the network in duplicate to insure reliable delivery to the central station.
In addition, the Scanner is responsible for supervising reporting a STU malfunction or a problem with the telephone line (such as a disconnected line). Information regarding STU status is sent by the Scanner to the Message Switch.
The RScanner is an optional component in the network which is used as an extension to the Scanner. Many telco central offices are small and do not require the STU capacity of a full Scanner. An RScanner is ideal for these locations. It is much smaller and less expensive, with a capability of handling 1 to 96 STUs. However, it is not a stand-alone unit. It must be linked to a Scanner at a remote location (another central office) by means of a two-wire data line and a special plug-in card for the Scanner.
The telcosí use of a mix of large Scanners and small RScanners is transparent to the alarm central monitoring station.
The Message Switch is the hub of the network. It consists of a pair of minicomputers that are cross-linked to provide back-up reliability. The Message Switch is typically installed in a telco minicomputer operations center or central office. It communicates with Scanners (up to 95) at many different central offices, in much the same manner as the Scanner communicates with many STUs. STU messages from the Scanner are logged to magnetic tape by the Message Switch and routed to the proper central monitoring station.
The Message Switch is dedicated to communicating with Scanners and central station equipment. A database is included to keep track of alarm dealers and the STUs assigned to them, as well as the operating characteristics of each STU. As messages are received from the Scanners, a database is interrogated for ownership of the STU. Once the owning central station is identified, the message is passed to the equipment for processing at the central station. Similarly, messages from the central station are routed to the proper STU.
- DERIVED CHANNEL RECEIVER -
The DERIVED CHANNEL RECEIVER (DCR) consists of a pair of PC's with a software package designed by DCX Systems and listed by Underwriters Laboratories for monitoring high risk burglary and fire applications. Its primary function is to interface the central monitoring station to the DCX System's Message Switch.
The Message Switch interrogates (polls) the DCR every few seconds for data which it may have to send into the network. (At the same time, if the Message Switch has data for the DCR, it will be sent along to the DCR with one of the interrogations.) This constant handshake can be seen by the alarm dealer by observing a pair of light emitting diodes (LEDís) flashing on the front panel of the modem.
The DCR converts messages it receives from a machine based language used by the Message Switch into English text, which it displays on the terminal. Likewise, any dealer response entered at the keyboard is converted to machine language and sent to the Message Switch.
A printer is attached to the DCR and provides a paper log for all alarm traffic going to and from the central monitoring station. This can be used as an audit trail should one be required by the monitoring station.
Refer to Figure 2 for a diagram of the equipment required in the alarm central monitoring station for a redundant configuration. Connection to the Message Switch is by way of two (2) private data circuits provided by the telephone company. These circuits appear to the alarm dealer as telco 4-wire loops.
Each telco loop is connected to a modem that translates electrical signals compatible with telephone equipment into those compatible with computer equipment.
DERIVED CHANNEL RECEIVER
- FEATURES -
A Local Database is provided and maintained on the hard drive. Network information, specific to each of the alarm account, is extracted from the database and presented to the user in an easy to view format. Also, the DERIVED CHANNEL RECEIVER (DCR) is capable of comparing some of the information stored within the network to that desired by the dealer and reporting any discrepancies found.
User Friendly Menus provide easy access to network functions. Users are not required to memorize cryptic syntax commands. The user need only select a desired function from a menu of items. The DCR will automatically prompt the user for any additional parameters required to complete the desired function.
A "Message Watch" feature allows the alarm dealer to program certain messages into the DCR that will trigger an audible alarm should the message be received from the network. This allows the dealer to be notified of certain network alert messages.
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