BCoFD Radio Overview
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BCoFD Radio Overview

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  • A talkgroup is a group of users that have a common need to communicate.
  • Your “Sarah” is called the Zone Controller. Sarah has two primary functions. The first is to ensure that only radios programmed to work on the RISCON system are allowed to use the system and the second is to control the distribution of the frequencies kept in the pool.
  • The backbone of a Motorola trunked radio system begins with a series of trunked repeaters. One repeater always has the duty of transmitting and receiving the data traffic required to monitor and control the operation of the system. This repeater (channel) is called the control channel. Every tower has a designated control channel. The control channel’s primary function is to keep track of the selected talkgroup of every radio affiliated with the tower. The control channel never carries voice traffic. Therefore, if you have a 5 channel system, only 4 voice transmissions can occur simultaneously.
  • If you are using Push to Talk Tones, this is an example of what occurs between the time you press the PTT button and you hear the tones (about ½ second). NOTE: If you are not using PTT tones, the same process occurs during the first ½ after pressing the PTT button.
  • When the conversation is complete, all of the radios return to the control channel. This process can occur multiple times during the transmissions of a specific conversation. If there are times in the transmissions when no radio is keyed, the radios return to the control channel. The radio users never know the specific channel they are assigned. They just need to know that if they are selected to the same talkgroup on their radio, that they can communicate with all other radios selected to the same talkgroup that are affiliated with the system.
  • Trunking systems are designed based on the concept that it is highly improbable that a large percentage of users will key up at exactly the same time and that most conversations are relatively short. Your system has a “Time out Timer” set to 60 seconds. What that means is that if the radio user presses and holds the PTT button continuously for 60 seconds, at 56 seconds they will begin to hear a tone, and at 60 seconds, Sarah will take the channel away from the user. This is designed primarily for the radio that gets lodged down beside the seat with the mic keyed. This means that a frequency will not be locked out of the pool for longer than 60 seconds (demonstrate tone).
  • In a trunking system, only one radio can transmit at a time. If a radio is transmitting on a specific talkgroup and another radio keys up on the same talkgroup, the second user will hear a “Prohibit Tone” (demonstrate tone). The user should de-key the radio and listen. If they hear on going conversation, the user should wait for the transmission to end and then re-key the radio. If no conversation is heard, the user may be out of range on the system. Out of range will display on the radio (demonstrate tone).
  • System busy means that all frequencies have been assigned and “Sarah” has no frequencies remaining in the “pool” to assign. When this occurs the user receives a System Busy Tone (demonstrate tone). The user should de-key the radio. Sarah puts the radio user’s request into a queue and when a frequency is available, Talk Permit Tones (demonstrate tone) are sent to the radio. After the user receives the Talk Permit Tone, they have 3 seconds to key up the radio or Sarah will assign the frequency to the next user in the queue. NOTE: If the user re-keys the radio before receiving the PTT tones, their initial request is cancelled and they are then placed back in the queue.
  • Describe how radios and dispatch consoles will perform when a site is in Site Trunking.
  • Describe how radios and dispatch consoles will perform when a site is in Failsoft.
  • Describe how radios and dispatch consoles will perform when a site is in Failsoft.

BCoFD Radio Overview BCoFD Radio Overview Presentation Transcript

  • BALTIMORE COUNTY Motorola Trunking Radio System Overview
  • Baltimore Co Trunking System
    • - Project 25 Compliant - Standards for digital radio communications so agencies can communicate with mutual aid response teams in emergencies
    • - All Digital - Improves clarity & voice quality
    • - Simulcast System – Offers a larger coverage area
    • - Increased Frequency Availability
      • Multiple Talkgroups/Channels per entity
      • Eff icient use of frequencies (Channels are only used when Talkgroup members are transmitting).
      • 2 Zones - North - South
      • 18 Tower Sites
      • - Nationwide Emergency Interoperability
      • Public Safety Nationwide frequencies
    • - Emergency Alerting Capability
    • - Voice Encryption (Secure)
  • North Simulcast Site (3 tower sites/12 channels) Route 439 Spook Hill Hereford (Prime Site) South Simulcast Site (15 tower sites/24 channels) Arcadia MEMA Warren Jacksonville Red Run Fire Headquarters (Prime Site) Hickey Kingsville Highway Shop 2 Essex Allender Catonsville North Point Brady Avenue Sparrows Point Backup Prime Site for Both the North & South Simulcast system Gilroy BALTIMORE COUNTY TOWER SITE LOCATIONS
  • THE NEW P25 SYSTEM
    • Digital Trunking
      • A digital radio transmitter processes sounds into patterns of numbers, or "digits"
      • Frequencies are pooled and assigned when the radio user presses the PTT button
      • Advantages
      • Users have access to more Talkgroups/Channels
      • Utilizes idle frequencies and frequencies are available to all users
  • TRUNKING In two-way radio communications, Trunking refers to the automatic and dynamic sharing of a small number of radio channels among a large number of radio users. A Trunking System efficiently distributes message traffic across the available channels and reduces wait time for those channels.
  • Talkgroup A Police 1 2 3 4 5 Trunking allows individual users to be combined into Talkgroups . A TALKGROUP is a group of users that have a common need to communicate with each other in order to accomplish their job. Talkgroups Talkgroup B Fire/EMS
  • The Motorola Trunked radio system uses a computer called the Zone Controller as an “operator”. The Zone Controller has 2 PRIMARY DUTIES: FIRST, to insure that only radios programmed for your specific Trunking system are used on the network. SECONDLY, to maintain and distribute the frequencies or channels on the network. Zone Controller
    • One of the frequencies/channels at each tower site is programmed to
    • operate as the CONTROL CHANNEL.
    • The Control Channel’s job is to keep track of the radios affiliated
    • with each tower and know which Talkgroup/Channel is selected
    • on the radio.
        • If I turn the Talkgroup/Channel selector one click, my radio sends
        • two messages to the control channel. “I am leaving this
        • Talkgroup/Channel and I am arriving at the newly selected
        • Talkgroup/Channel”.
    • The Control Channel carries only data and cannot be used for
    • voice communications.
    Control Channel
    • When you turn your radio on, it affiliates with the network through the Control Channel on the site nearest your location.
    • When no one is transmitting on your selected Talkgroup/Channel, your
    • radio is still “talking” to the Control Channel. (Note: This transmission is
    • transparent to the user.)
    • Your radios may be programmed with “Talk Permit Tones”.
    • You should not begin your transmission before you hear the tones.
    Turning On Your Radio
  • Step 1: The following is an example of what occurs between the time you press the PTT (Push-to-Talk) button and the time you hear the Talk Permit Tones (less than ½ second). In this example, Channel 1 is the Control Channel and Channels 2 through 5 are voice channels. When you press the PTT button, the Control Channel receives the request and forwards the request to the Zone Controller that a radio is on. Talkgroup/Channel “B” wants to talk to all other users on the system selected to the same Talkgroup/Channel. Call Processing Event Sequence
  • The Zone Controller then communicates with the Control Channel at every tower and asks if they have any radios turned to Talkgroup/Channel “B” affiliated on their site. Based on the replies from the Control Channels, the Zone Controller reaches into the pool and chooses a specific frequency for the transmission. In our example, this is Channel 5. The Zone Controller then sends a message to all of the Control Channels that if they have any users selected to Talkgroup/Channel “B”, they should send those users to Channel 5. Step 2: Step 3: Step 4: Step 4 Call Processing Event Sequence (Con’t)
  • All radios monitoring the Control Channel receive this message and travel over to Channel 5. Step 5: Voice Call Processing Event Sequence (Con’t)
  • Step 6:
    • When the transmission is completed, all of the radios selected to Talkgroup/Channel
    • “ B” automatically return to the Control Channel.
    • The previously assigned voice channel returns to the pool and is available for other
    • transmissions. ( NOTE: This process may occur multiple times during a conversation and is
    • transparent to the radio users.)
    • The radio user never knows what specific frequency they are transmitting on and
    • they don’t care. They are primarily concerned that they can transmit to and receive
    • from other radio users selected to the same Talkgroup/Channel.
    Voice The Zone Controller promises the radio users that if they are selected to the same Talkgroup/Channel and affiliated with any tower on the system, they will be able to communicate with each other. Step 6: Call Processing Event Sequence (Con’t)
    • Trunking systems are designed or sized based on the concept that:
    • It is highly improbable that a large number of users will want to transmit at exactly the same time.
    • It is important to remember that whether you have two radios or 200 radios selected to the same Talkgroup/Channel, they only use one frequency.
    • And that most conversations are relatively short.
      • The system has a “Time out Timer”
      • set to 30 seconds. If you have the
      • PTT pressed continuously for
      • 26 seconds, you will begin to hear
      • a dull tone. At 30 seconds, the
      • Zone Controller will take the
      • channel away from you. Your
      • transmission will no longer be
      • heard and you must release the PTT and press it again for the radio to receive a new channel assignment.
    Trunking System Design
  • The first tone is a “Talkgroup/Channel Busy” What is a “Talkgroup/Channel Busy”? When a radio user attempts to key up their radio and the Talkgroup/Channel where they are selected is already transmitting (i.e.“talkover” another user), they will receive a “Talkgroup/Channel Busy” prohibit tone. There are two types of “Busy” tones that you may receive on the trunking system. Trunking System Design (Con’t)
    • What should I do if I hear a “Talkgroup/Channel Busy” tone?
    • Release the PTT button and listen for other transmissions.
    • When the transmission ends, press the PTT button, wait
    • for the “Talk Permit” tones then begin transmitting.
      • N OTE: The radios also “hang” around on the channel for a few seconds
      • after the user releases the PTT. During this “hang time” no
      • transmission is heard.
    • If this occurs, wait a few seconds and press the PTT.
    • Also,
    • You will hear the same tone when you are out of range of the trunking
    • system. In this case, in addition to the tone, an “OUT OF RANGE” message
    • will appear on the display of your radio.
    Trunking System Design (Con’t)
    • The second tone is a “System Busy” tone
    • What is a “System Busy” tone?
    • If the radio user presses the PTT and no channels are available for assignment, the user will receive a “System Busy” tone.
    • What should I do if I receive a “System Busy” tone?
    • Release the PTT button and wait for the three quick Talk Permit
    • Tones. Within three seconds of hearing these tones, press and hold the
    • PTT button to transmit your message.
    • NOTE: After receiving the Talk Permit Tones, the radio user must press the PTT within three seconds or the channel will be reassigned to the next user in the queue.
    Trunking System Design (Con’t)
    • Trunking Systems contain many layers of redundancy or “back-up” to ensure that communications continue even in extreme situations.
    • Back-up modes that are transparent to the radio user are:
    • Rotation of Control Channels
    • Repeater “skipped” if off the air
    • Redundant communication methods
    • connecting infrastructure
    • Back-up modes that are visible to the radio user are:
    • Site Trunking
    • Failsoft
    Introduction to Radio System Back-up Modes
    • How does this affect the radio user?
    • Radios operate as they would in a normal Trunking environment
    • The radio will display “Site Trunking”
    • You will have PTT tones
    • You will still be able to communicate with users in your Zone
    • (you will not be able to communicate with users in other Zones)
    • Your EMERGENCY button will work, but may not be displayed on the console in the Dispatch Center
    • Communication with your Dispatch Center may be limited
    Site Trunking - The Zone Controller has lost communications with the Site(s). Site Trunking
    • Examples of Major Failures :
    • Both Zone Controllers Fail
    • All Four Control Channels Fail
    • All Voice Channels Fail
    • What happens to the radios in Failsoft?
    • Radios operate as they would on a conventional repeater system
    • Each channel is mapped to a specific frequency
    • A low level alert tone is broadcast every 10 seconds
    • “ FAILSOFT” is displayed on the radio
    • PTT Tones are not available
    • You will hear transmissions from multiple Talkgroups on your Channel
    • The Emergency button functionality is not available
    • What should the radio user do?
    • If you are on the Talkgroup/Channel where you should be assigned, leave the radio
    • where it is selected and listen for transmissions.
    • If not, you should select the Talkgroup/Channel where you should be assigned and listen for transmissions.
    Failsoft at the Zone Level – The Zone Controller has failed. ( This occurrence is extremely rare.) Failsoft
    • Examples of Major Failures :
    • Both Zone Controllers Fail
    • All Four Control Channels Fail
    • All Voice Channels Fail
    • What happens to the radios in Failsoft?
    • Radios operate as they would on a conventional repeater system
    • Each channel is mapped to a specific frequency
    • A low level alert tone is broadcast every 10 seconds
    • “ FAILSOFT” is displayed on the radio
    • PTT Tones are not available
    • You will hear transmissions from multiple Talkgroups on your Channel
    • The Emergency button functionality is not available
    • What should the radio user do?
    • If you are on the Talkgroup/Channel where you should be assigned, leave the radio
    • where it is selected and listen for transmissions.
    • If not, you should select the Talkgroup/Channel where you should be assigned and listen for transmissions.
    Failsoft at the Zone Level – The Zone Controller has failed. ( This occurrence is extremely rare.) Failsoft