Police Use Voice & Data Platform for Radio System

Situation

A Midwest communications company specializing in 2-way Radio Systems needed to create a communications link to transport Ethernet, Analog and Dry Contact Channels between a county dispatch center and a police department radio control center.

The Ethernet channels would be used for police administration and the Analog and Dry Contacts over Ethernet were needed to operate a Police Public Safety Radio System. The dry contacts were needed to key the transceiver to either transmit or receive because transporting the original radio system’s pilot tone signals over Ethernet encountered interference issues.

As a result, one dry contact channel was required along with each analog signal. Eight 4-wire and four 2-wire analog circuits were needed to connect to a Signal-to- Noise Voter and Dry Contacts were needed to switch between Receive and Transmit on the 2-Way Radio.

The two control centers were linked by a leased fiber optic data path that connected to a Multi-Service Provisioning Platform (MSPP) and JumboSwitch’s at each site. A JumboSwitch10/100/1000M Ethernet card connects to the Police network.

The goal was to find a managed, all-in-one-box Ethernet network solution that was both reliable and cost efficient.

Solution

Enlarge Diagram

Online research turned up a couple of low-end 1 or 2-channel Analog-over-Ethernet devices, but it was clear that the most viable multi-channel Ethernet, Analog and Dry Contact solution for this application was the TC Communication’s JumboSwitch Ethernet, Voice & Data Platform.

In addition to offering all interfaces in one chassis, the JumboSwitch offered Ethernet Port rate limiting, management and self-healing ring redundancy. Because the entire Police Department only leased a total of 50 Mbps of bandwidth, the JumboSwitch’s rate limiting feature was crucial. It boosted bandwidth efficiency and enabled the leased fiber to be proportionately shared between radio other departmental network traffic (30 Mbps was required for Ethernet traffic and 20 Mbps for radio traffic).

Two 4U JumboSwitch chassis, one at the county dispatch center and one at the police department, were deployed adjacent to the MSPPs (see diagram below). The JumboSwitch’s Analog and Dry Contact interface cards connected to a Motorola 2-Way Radio System on the County Dispatcher side and to a voter on the Police Department side. (The voter uses digital signal processors to continuously select the receiver with the best Signal-to- Noise Ratio from multiple remote sites).

Each chassis was equipped with three 8-port Analog/ Dry Contact interface cards (TC3846-6) and one 6-port 10/100/1000 Ethernet Card (TC3841). The Analog and Dry Contact cards provide eight 4-Wire 600Ohm analog ports, four channels of 2-Wire 600Ohm analog and 12 channels of bi-directional dry contacts to key the microphone / transmitter.