Remote control: The sentry that never sleeps
Downtime, costly maintenance and emergencies can be limited with the use of the right remote control and monitoring equipment.
Even before Tom Sawyer found a way to remotely whitewash Aunt Polly’s fence, people have looked for ways to avoid expending labor and to expedite problem solving. The combination of wireless communications and DTMF tone signaling has led to systems that reduce labor and maintenance costs, speed notification of problems and increase maintenance efficiency.
Remote systems perform both active tasks, such as base station and repeater control, and passive tasks such as data acquisition and situation monitoring. The remote control marketplace offers a variety of applications for mobile communications.
Tone remotes Tone remote controls are usually desktop instruments with a DTMF keypad and handset resembling a telephone. Systems are generally dedicated to a specific make of base station. Units can control one to four base stations or repeaters from a single instrument. Frequently used by dispatchers, most contemporary units have liquid crystal displays for numeric and alphanumeric characters. The use of text aliases programmed into the LCD eliminates operator confusion and simplifies training.
Other information provided can include frequency selections (for at least eight frequencies) and pager capcodes. Remotes can be equipped with a built-in paging encoder and a database. This allows two-tone, five-tone, DTMF and alert paging. The database provides name verification of the paging selection, allows users to scroll through preprogrammed pager codes and names, and provides the option for stack paging of multiple users. Programmable soft key functions, display text, guard tones and function tones can be defined in the field.
Digital signal processing (DSP) removes disruptive chirps or function tones, allowing users to speak immediately without waiting for tones or key-up delays. Parallel status indication features allow the remote to reflect the true status of the base station, regardless of how many parallel remotes are tied to the base station. When the base station status is changed, the change can be displayed on all parallel remotes. Configuration programming can also be cloned from one remote to another or to all remotes on the system. Optional features on tone remotes include intercom, privacy and supervisor takeover.
Multiple applications Remote systems can be used for fixed data, mobile dispatch, automatic vehicle location (AVL) and credit card verification in remote locations. The central component is a remote network processor, which is positioned between a company’s host computer and the radio infrastructure. Other components are mobile data controllers, which attach to a remote radio or mobile computing device and function as a radio modem.
Such remote control devices allow utilities to remotely control critical functions via their paging infrastructure. For example, an electrical utility can control its capacitor banks through four control channels. Motor-driven switches can be controlled by using a simple two-channel controller. Limit timers, lockout timers and even voltage sensors with set periods of lockout can be programmed to activate when adverse conditions are sensed. LCD counters can track the number of activations or aborts requested by the control center or implemented by the remote’s own internal microprocessor. Controls such as this usually have non-volatile memory backup for storing system configuration and can retain data for years. Timers can be configured for more than 100 hours of duty, and counters can count as many as 999,999 cycles.
AMR Another remote primarily affecting utilities is automated meter reading. A network of remotes can offer options such as daily peak and off-peak billing by means of real-time meter reading and cycled readings. Customer service can also be disconnected remotely from the main office instead of dispatching a field technician. Power outages and attempts to tamper with service can be spotted instantly, allowing utilities a head start on restoring service.
SCADA Supervisory control and data acquisition (SCADA) systems generally include a radio transceiver, RS-232 modem interface and a digital and analog I/O board. The number of available inputs varies among manufacturers, but most systems provide both analog and digital inputs as well as contact closure output lines. The common speed for modems is 9,600bps. Internal memories can hold as many as 64 programmed RF channels. Available features include error detection and compatibility with Microsoft Windows for logging site activity to standard database files. SCADA modules generally consume little power, as low as 80mA at 12Vdc, and they can operate on one-way or two-way radio systems.
Testing, monitoring and alarming Automatic monitoring is superseding the practice of constant human monitoring of services such as a paging system. Remote-controlled switches allow a provider to avoid system-wide failures because of a failed control link or paging transmitter. The switches send test messages over the network at regular intervals for automatic decoding by an automatic monitor connected to an alarm. Both alphanumeric and numeric POCSAG messages can be monitored in this fashion.
Paging system testers can also dial a paging terminal at predetermined intervals to activate a pager connected to the test system. The tester detects when the pager receives the signal and resets its interval timer until the next page. If the page is not delivered within the specified time, the tester automatically sends a message to the phones or pagers of appropriate personnel to indicate the need for system maintenance. Some systems allow for the maintenance personnel to use DTMF tones to acknowledge the error notification or deactivate the alarm.
Remote monitors that check contact closures also use paging services to forward notification of alarms or situations. Systems are available for either alphanumeric or numeric pagers, and features such as automatic redial and backup pager numbers are available. Control points and other functions can be operated from a DTMF phone. Remotes can also provide dial-up control for small alarm networks.
Several formats for notification are available. Remote monitoring paging systems can be designed to page specific individuals or groups with preprogrammed alphanumeric alarm messages. Some paging alarm systems send a text message fully describing the nature and location of the alarm condition. Systems can be as basic as two contact closure points or provide as many as 48 closure points. Internal dial-up modems can be provided to send notifications via a wide-area paging service. For campus situations where the party to be notified is physically proximate, optional small transmitters, typically 4W or 5W, are available for local paging.
Some monitors provide for as many as 240 alarm conditions of all types, including ac or dc power levels, SWR, insertion loss, temperature, intrusion, fire alarm, tower light status, RF power, battery voltages, current drain, and shelter environmental conditions. Alarms can be monitored, announced and acknowledged over telephone lines, mobile radio systems, alphanumeric pagers, RS-232 ports and cellular telephones. Systems are even available with internal microphones, complete with a built-in compression filter, for remote monitoring of site audio.
Some of the most recent monitor products introduced can compare measured data against operator-selected alarm limit and perform a predetermined action on site using relay contact closures. Alerts can be sent via wireline PSTN with data reports and can be tagged for one to four recipients. Modular, expandable systems have been designed for trunked radio systems, conventional radio, paging, cellular, IMTS, mobile radio dispatch and aviation. With an expansion slave unit, some models can be expanded to handle as many as 64 transmitters or antennas. Some new models offer virtually instantaneous processing of input channels at intervals of every quarter of a second.
Barnett Engineering, 7710 5th St., S.E., #215, T2H 2L9, Calgary, Alberta, Canada, 403-255-9544, [email protected] BayTech, 200 N. 2nd St., Bay St. Louis, MS 39520-4536, 403-933-5393. CPI Communications, 1186 Commerce St., Richardson, TX 75081-2307, 972-437-5320. Decibel Products Division of Allen Telecom Group, 8635 Stemmons Freeway, Dallas, TX 75356-9610, 214-631-0310, www.allentele.com. DPS, 4922 E. Yale Ave., Fresno, CA 93727-1517, 209-454-1688. Eagle Telecom International, 910 Gemini St., Houston, TX 77058, 713-280-0488. IDA, 1345 Main Ave., Fargo, ND 58103-1631, 701-280-1122, ida [email protected] Midian Electronics, 2302 E. 22nd St., Tucson, AZ 85713-2000, 520-884-7981, [email protected] Padcom, 2045 City Line Road, Bethlehem, PA 18017, 610-882-9940. PageTap, 8200 E. Pacific Place #204, Denver, CO 80231-3212, 303-337-4811. RF Industries, 7610 Miramar Road, San Diego, CA 92126-4202, 619-549-6340, [email protected] compuserve.com. SynetCom Digital, 1426 Aviation Blvd. #203, Redondo Beach, CA 90278-4062, 310-379-2000. Utility Network Services, P.O. Box 850461, Richardson, TX 75085-0461, 214-234-5935. Visiplex, 1141-G Lake Cook Road, Deerfield, IL 60015-5235, 847-405-0771. Zetron, P.O. Box 97004, Redmond, WA 98073-9704, 206-820-6363, www.zetron.com.
