- 1. BALTIMORE COUNTY Motorola TrunkingRadio System Overview
2. Baltimore Co Trunking System
- - Project 25 Compliant- Standards for digital
radiocommunications 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).
-
- - Nationwide Emergency Interoperability
-
- Public Safety Nationwide frequencies
- - Emergency Alerting Capability
- - Voice Encryption (Secure)
3. North Simulcast Site (3 tower sites/12 channels) Route
439Spook HillHereford (Prime Site) South Simulcast Site (15 tower
sites/24 channels) ArcadiaMEMA WarrenJacksonville Red RunFire
Headquarters (Prime Site) HickeyKingsville Highway Shop 2Essex
AllenderCatonsville North PointBrady Avenue Sparrows Point Backup
Prime Site for Both the North & South Simulcast system Gilroy
BALTIMORE COUNTY TOWER SITE LOCATIONS 4. THE NEW P25 SYSTEM
-
- 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
-
- Users have access to more Talkgroups/Channels
-
- Utilizes idle frequencies and frequencies are available to all
users
5. TRUNKING In two-way radio communications,Trunkingrefers 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. 6. Talkgroup A
Police 1 2 3 4 5 Trunking allows individual users to be combined
intoTalkgroups . ATALKGROUP 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 7. The Motorola Trunked radio
system uses a computercalled theZone Controlleras an
operator.TheZoneController has 2 PRIMARY DUTIES: FIRST,to insure
that only radios programmed for yourspecific Trunking system are
used on the network. SECONDLY,to maintain and distribute the
frequenciesor channels on the network.Zone Controller 8.
- One of the frequencies/channels at each tower site is
programmed to
- operate as theCONTROL CHANNEL.
- The Control Channels job is to keep track of the radios
affiliated
- with each tower and know which Talkgroup/Channel is
selected
-
-
- 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
- The Control Channel carries only data and cannot be used
for
Control Channel 9.
- 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 10. 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
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 11. 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
messageto all of the Control Channels that if they haveany 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 (Cont) 12. All radios monitoring the Control Channel
receive this message and travel over to Channel 5. Step 5: Voice
Call Processing Event Sequence (Cont) 13. 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 dont 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
withanytower on the system, they will be able to communicate with
each other. Step 6: Call Processing Event Sequence (Cont) 14.
- 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 atexactly 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 aTime out Timer
-
- set to 30 seconds. If you have the
-
- PTT pressedcontinuously 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 15. The first tone is aTalkgroup/Channel
Busy What is a Talkgroup/ChannelBusy? When a radio user attempts to
key uptheir radio and the Talkgroup/Channelwhere they are selected
is alreadytransmitting (i.e.talkover another user),they will
receive a Talkgroup/Channel Busyprohibit tone. There are two types
of Busy tones that you may receive on the trunking system.Trunking
System Design (Cont) 16.
- 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 timeno
- If this occurs, wait a few seconds and press the PTT.
- 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 (Cont) 17.
- 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 (Cont) 18.
- 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 visibleto the radio user are:
Introduction to Radio SystemBack-up Modes 19.
- How does this affect the radio user?
- Radios operate as they would in a normal Trunking
environment
- The radio will display Site Trunking
- Youwillstill 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 onthe
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 20.
- Examples of Major Failures :
- Both Zone Controllers Fail
- All Four Control 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 21.
- Examples of Major Failures :
- Both Zone Controllers Fail
- All Four Control 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