Many transit systems optimize telecom costs with a private branch exchange (PBX), a company-owned telephone system in which users can communicate on local lines, while sharing a limited number of external phone lines. The PBX is owned and maintained by the transit system rather than the telephone company.
PBX Benefits
- Cuts Costs: The main purpose of a PBX is to save the cost of requiring a line for each user to the telephone company's central office.
- Saves Time: In the past, receptionists connected inbound and outbound calls manually. This process wasted up to 45 seconds per call to connect. Today, connections are made almost instantaneously via electronic call-routing present in PBX.
- Increases Efficiency: An Internet-based PBX system eliminates the need for long distance service and is flexible and easy to set up and maintain.
- Enhanced Conference Calling: Call quality is better in a PBX system versus a traditional telephone system, enabling employees to enjoy better, clearer conference calling.
- Easy to Expand: A PBX phone system provides an intuitive interface and is easy to expand as business needs change.
PBX Components
- The PBX’s internal switching network
- Microcontroller or microcomputer for arbitrary data processing, control and logic
- Logic cards, switching and control cards, power cards and related devices that facilitate PBX operation
- Stations or telephone sets, sometimes called lines
- Outside telecommunication trunks that deliver signals to and from the PBX
- Console or switchboard to control incoming calls
- Backup power system consisting of sensors, power switches and batteries
- Interconnecting wiring
- Cabinets, closets, vaults and other housings
The Backup Power System
The primary use of the battery backup system is to keep the PBX system operating during a power failure. Other ways that the battery backup system can offer protection is during:
- Lightening strikes
- Power surges from motors and equipment being switched on and off
- Power spikes and sags
- Electrical noise or high frequency disruption from nearby equipment
- Frequency instability
- "Harmonic distortion," which may affect audio quality
Periodic maintenance of the system is required for optimum performance. This includes replacement of the backup batteries.
PBX System Upgrade: A Step-by-Step Guide
Recently, a transit system sought to retain a contractor to remove, dispose and install batteries at eight PBX locations within its service area and to install battery disconnect switches at four PBX node locations.
Many of the previous batteries had failed prematurely, lasting only 12 to 16 years — just three-quarters of their life expectancy — due to the hot operating environment. The issue was addressed and changes were made to the environmental systems at these locations.
After careful analysis, the battery procurement and installation was outsourced. The bid invitations specified valve-regulated lead-acid (VRLA) batteries, plus labor, material and equipment necessary to remove, dispose and install the new backup system.
The battery manufacturer and its exclusive distributor performed all services, working together as a single vendor. This provided a single point of contact for the customer for easier project management. As a reference for other companies who are installing or replacing their PBX batteries, here is an outline of the steps involved in the process.
Initial Walkthrough: EnerSys and its distributor National Railway Supply performed a comprehensive site survey, evaluating the battery environment for anything that might impact battery performance and longevity, such as temperature, moisture and contaminants. They also assessed the space requirements and rack placement to ensure that the batteries could be easily accessed for future service and to ensure that there were no safety concerns.
Battery Selection and Sizing: The team recommended a battery solution designed specifically for communication applications. The selected VRLA batteries featured thick positive plates for long life and recombinant technology. Other features included a welded/epoxy, dual post seal design for high integrity seal, large copper post design for high rate performance and protective steel cans to maintain constant, uniform compression for the life of the cell.
The team also re-evaluated the size of the batteries needed. This is important as both application demands and the size of the manufacturer’s product can change during the 10- to 20-year life span of the batteries. In terms of the application, the number of phone lines and devices may have increased, as well as the amount of electrical noise and system disruptions, requiring more battery power. Regulations also may have changed over time, requiring backup systems to provide longer standby coverage duration during crisis situations. For these reasons, it is important to accurately assess your power needs when changing over to new batteries.
Install Redundant Batteries: Calculating accurate run times is also important for determining the amount of battery coverage that is required in the interim stages when temporary batteries are installed to back up the system prior to actual installation. Using these assessments, the team determined the required runtimes and switched the system from the old batteries to temporary units.
Install Battery Disconnect Switches: The team installed battery disconnect switches for workability, allowing them to switch between the main and secondary batteries in case of a battery failure and for future routine maintenance.
Run Cables: With the disconnect switches in place, the team installed the new cables, connecting the power source to the bus to the temporary standby batteries. They then switched the system over to the main batteries.
Battery Removal and Recycling: Lead acid batteries are highly recyclable. Recycling centers can recover more than 98 percent of the lead and plastic in a lead acid battery. Once those reclaimed materials reach a battery manufacturer, they can account for 60 to 80 percent of the lead and plastic in a “new” lead acid battery. Recycling is a closed-loop process that can continue indefinitely, meaning that components that make up these batteries can be reused many times.
Battery end-users are responsible for the proper disposal of their batteries, and there are many state and federal laws governing battery recycling. If a battery is dumped in a landfill or shipped to a recycler that does not handle it properly, the end user may be held responsible for any resulting cleanup costs or environmental damage. For this reason, it is critically important that batteries are handled properly. In this case, the team removed the old batteries and delivered them to an EPA-compliant recycling center. The recycling center provided the transit authority with cradle-to-grave documentation that detailed the nature of the waste, the registered carrier and the licensed final destination or recycling process.
System Testing: Lastly, the team tested the new batteries to ensure that they were working properly and that they did not create any interference with the current system.
Jennifer A. Eirich is marketing manager, Utilities/Rail, at EnerSys. JD Beck is vice president of marketing and sales for National Railway Supply.
