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Case Study: Achieving an Interoperable Multi-Agency System for Mutual Aid Emergencies in Solano County

Author: Gary Correia

Copyright: 9-1-1 Magazine, Feature Content

Date: 2015-10-09
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Interoperable systems by their nature aren’t neat and tidy, and Solano County agencies all had individual systems operating on different frequencies with an array of equipment from multiple suppliers. The new system would have to support three frequency bands, provide uninterrupted coverage across wide areas, and establish a patching solution to link the various disparate radio systems


A new interoperable mutual aid to allow multiple Solano County (CA) emergency response agencies to communicate in-county and without, especially when working joint agency emergencies such as local wildfires and major crime scenes. (Photo via Solano County Sheriff Facebook page, used by permission)


The investigations into the events of 9/11 and specifically how the emergency services dealt with the tragedy caused a ripple effect that saw authorities across the US, and the world, examine the communications infrastructure of their emergency agencies.

The issues highlighted in the wake of 9/11 weren’t unique to police and fire departments in New York: aging radio technology and equipment, a lack of interoperable communications between emergency responders and unreliable coverage in high risk areas were themes that many recognized.

Solano County, in northern California, was one of many regions that put their own emergency communications and disaster response planning under review. The Solano Emergency Communications Activity (SECA) group was formed in 2004 and comprised members from the region’s emergency services agencies as well as other key stakeholders.

SECA’s objectives were to determine the County’s needs and formulate a plan to put in place an interoperable radio system that would operate across the entire county in the event of mutual aid emergencies and disasters. With grant funding behind them, the team went out with an RFP and began the process of designing and selecting a system.


Building the System

Interoperable systems by their nature aren’t neat and tidy, and Solano County agencies all had individual systems operating on different frequencies with an array of equipment from multiple suppliers. The new system would have to support three frequency bands: VHF, UHF T-band and 800MHz. The system required a simulcast design to get uninterrupted coverage across wide areas, and a patching solution to link the various disparate radio systems, ultimately enabling agencies to work seamlessly on incidents that spanned different jurisdictions.

Left: Solano County's most recent Communications on Wheels truck was purchased with a grant from the California Department of Water Resources to improve the communications in the San Francisco Bay Delta region during emergencies. Part of a $5M project that includes five counties in the legal delta, the vehicle can provide cellular, internet, and multiple channel radio interoperability so that first responders can communicate with each other despite having different equipment. Managed by the Solano County Communications Department with grant management handled by the Solano County Sheriff's Office of Emergency Services, the vehicle also supports state-wide mutual aid, as seen here at 2015’s Wragg Fire in neighboring Napa County.

After a couple of false starts with the initial proprietary interoperability components, the first system that the team chose had a number of challenges and never went online.  The SECA team then focused their attentions on the capabilities of one of the system components, the Simoco Solar 2 Traffic Manager. The County learned that the Simoco equipment that they had initially invested in for just managing the TX side of the simulcast system could actually be used as the complete radio system and interoperability solution. Besides the robust transmit simulcast component, the system also provided system audio transport over IP, receiver voting, and a dispatch console priority input, all operating over a standard IP backbone. Ross Cardno, the Communications Supervisor for Solano County began to design a system that used the capabilities of the Simoco Solar 2 Traffic Manager and Network Interface units with their existing repeaters to build an interoperable wide area simulcast, multi-channel network.

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Choosing to re-design and build the interoperable simulcast system with Simoco’s simulcast technology as the foundation, and use the existing repeaters, the County was able to create a cost effective nine site (and expanding) system with 19 communications channels, supporting various County agencies including local sheriffs, city and district fire departments, and public works.

Ross Cardno needed to be able to maximize the use of the County’s slim grant funds: “We needed to solve our interoperability problem without having to spend tens of millions of dollars on new infrastructure and subscriber units,” he said. “Using Simoco’s simulcast solution, we were able to utilize our existing radio repeaters to build an inexpensive and affective interoperability solution.” 

A typical mutual aid event may have three channels patched together to allow 800MHz police units the ability to communicate with the UHF Fire units, and the VHF sheriff units.  Each agency may be instructed to switch to a specific channel for the event.  As an example, the police would switch to “Blue Tac 1,” fire units to “Red 3,” and sheriff units to “County 2;” the dispatcher would then carefully setup the correct patch.

The Solano County solution includes a fixed set of channels. Using the SECA acronym as the name for their channels, SECA channels 1, 2, and 3 were created with three mixed frequencies in each channel to enable interoperability between the different agencies using those specific bands.  The names for the channels are then common to all agencies.  During a mutual aid event such as a high speed chase that spans multiple cities, the various units can be dispatched to “SECA 1”.  All units from the various agencies, whether they are on an 800MHz trunked system or VHF or UHF conventional system, can select the same channel name on their radio and instantly start talking to all participants in the chase.


System Developments

Ross added: “Our original goal was to build a system of channels on different frequency bands that we could patch together.  What we found was that we could build a single channel on the Traffic Manager that included any repeater regardless of frequency. This allowed us to create a super channel with VHF, UHF, and 800 MHz components, providing a common communications platform complete with receiver voting and simulcast.”

With available interoperability funding, Ross’s team added a 700MHz P25 Phase 1 simulcast network to support regional mutual aid incidents. Because the County chose to continue using the Simoco simulcast technology for its new P25 digital network, it now became interoperable with the Simoco-based VHF, UHF, and 800MHz analog networks, as both simulcast systems share the same distributed IP architecture and system timing components.

“The absolute beauty of this simulcast system is that it operates completely over IP networks,” said Ross.  “With that flexibility, I am able to setup a mobile simulcast site instantly by activating my mobile hotspot from my smartphone.  This was really helpful during the Wragg fire that made national headlines.  We set-up our mobile communications vehicle near the fire to enhance the coverage of our existing countywide police and fire channels in the rugged terrain.  The improved coverage was pivotal in the evacuation of residents and their livestock from the area.”

The capability to link and add sites relatively easily and at a low cost has meant that the County can continue to expand and enhance its radio communications to meet the needs of their emergency services.


Solano County Emergency Services acquired this Mobile Communications unit through a Homeland security Grant in 2004. Manufactured by Farber Specialty Vehicles, the unit serves in- and out-of-county mutual aid as well as supporting mutual aid training, as shown here, during the annual California Mobile Command Center Rallies. (Photo: Left: Randall D. Larson; Right: Solano County Sheriff Facebook Page, used by permission)

Working together

The system continues to be a success, supporting the County’s emergency agencies in their day-to-day operations and when major incidents occur that require countywide support.

Ross also references the wide range of incidents that the system supports: “Wild fires aren’t the only event that can bring together multiple agencies in our county,” noted Ross. We also have a large air force base as one of our mutual aid partners operating on their own exclusive UHF trunked radio system.  Without our SECA mutual aid channels, we would really be in a jam to coordinate emergency services during a mass casualty incident.”

The system continues to expand as police and fire agencies request more sites. Because of its low cost nature – each new site only requires a Solar 2 Network Interface and RF equipment that links up with the rest of the system – expansion isn’t hampered by cost.

“We’re like every other county across the country – we have to cope with cuts to our budgets, but still provide the public with a high standard of emergency response and services,” Ross concluded. “You can use legacy equipment and bring it all together over IP without having to replace your entire communications infrastructure. This system fits the bill.”


Gary Correia is Vice President of the Americas Region at Simoco Group. Gary has over 20 years’ experience in the radio and communications sector, working with customers and partners across a wide range of industries and technologies including DMR, P25 and analog.

Simoco Group is a full lifecycle systems integrator and combines innovation with expertise to exploit the capabilities of IP and cloud based technology to deliver scalable, flexible and efficient critical communication solutions across P25, DMR and analog.  For more information, see:


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