DMR Application-Back to Back
Hytera Communications Co., Ltd
Global Customer Service Center
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Content
Part I What’s Back to Back?
Part II How Back to Back Works?
Part III How to Realize Back to Back?
Part IV FAQ
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Q1: I have two radios, one is analog, another is
digital, How to communicate each other?
Q2:I have two digital/analog radios, one is VHF,
another is UHF, How to communicate each other?
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Part I What’s Back to Back?
Definition
The “back-to-back” is a system solution on accessory pins. It is used to achieve
cross-band communication among analog and digital radios.
UHF
VHF
Back to Back
Analog Radio
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DMR Digital Radio
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Part II How Back to Back Works?
Work Principle(Mobile Radio)
Tx=Rx=f1
Tx=Rx=f2
R2
Tx=Rx=f1
R4
Tx=Rx=f2
R1
R5
MR 1
Tx=Rx=f1
Pin
Enable PTT
Audio Output
Pin
MR 2
Tx=Rx=f2
Tx=Rx=f2
Tx=Rx=f1
R3
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R6
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Part II How Back to Back Works?
Work Principle(Repeater)
Tx=f1
Rx=f2
Tx=f1
Rx=f2
Tx=f3
Rx=f4
R2
Tx=f3
Rx=f4
R4
R1
R5
Pin
Repeater 1
Tx=f2 Rx=f1
Enable PTT
Pin
Audio Output
Repeater 2
Tx=f4 Rx=f3
Tx=f3
Rx=f4
Tx=f1
Rx=f2
R3
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R6
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Part II How Back to Back Works?
Accessory Pin(Mobile Radio)
The mobile radios can be connected in a back-to-back manner as below
MR 1
MR 2
Ext Mic PTT
19
19
26
18
10
1
9
Audio
Output
Mic
26
18
10
1
9
Speaker Open Detect
Ext Mic PTT
Speaker Open Detect
Mic
Audio
Output
GND
1) Ground wire
To connect Pin2 of mobile radio1 and that of mobile radio 2.
2) Activation of mobile radio transmission
To connect Pin3 of mobile radio 1 and Pin16 of mobile radio 2.
To connect Pin16 of mobile radio1and Pin3 of mobile radio 2.
3) Audio signal output
To connect Pin8 of mobile radio 1 and Pin7 of mobile radio 2.
To connect Pin7 of mobile radio 1 and Pin8 of mobile radio 2.
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Part II How Back to Back Works?
Accessory Pin(Repeater)
Analog Repeater
Digital Repeater
Mic
19
19
26
18
10
1
9
Analog PTT
Carrier Detect
Slot-A Slot-B
26
18
10
1
Audio Output
9
Voice Detect
Digital PTT
Mic
GND
Analog
↔ Digital
1) Ground wire
To connect PIN2 of analog repeater and that of digital repeater.
2) Activation of digital repeater transmission
To connect PIN3 of analog repeater and PIN16 of digital repeater.
3) Analog audio output
To connect PIN8 of analog repeater and PIN7 of digital repeater.
4) Activation of analog repeater transmission
To connect PIN16 of analog repeater and PIN3 of digital repeater.
5) Digital audio output
To connect PIN7 of analog repeater and PIN24 or PIN25 of digital repeater.
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Part II How Back to Back Works?
Accessory Pin(Repeater)
Analog Repeater 1
Analog Repeater 2
Analog PTT
19
19
26
18
10
1
9
Carrier Detect
Audio
Output
Mic
26
18
10
1
9
Carrier Detect
Analog PTT
Mic
Audio
Output
GND
Analog
↔ Analog
1) Ground wire
To connect PIN2 of analog repeater 1 and that of analog repeater 2.
2) Activation of repeater transmission
To connect PIN3 of analog repeater 1 and PIN16 of analog repeater 2.
To connect PIN16 of analog repeater 1 and PIN3 of analog repeater 2.
3) Analog audio output
To connect PIN8 of analog repeater 1 and PIN7 of analog repeater 2.
To connect PIN7 of analog repeater 1 and PIN8 of analog repeater 2.
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Part II How Back to Back Works?
Accessory Pin(Repeater)
Digital Repeater 1
Slot-B
Slot-A
Digital Repeater 2
Slot-A Slot-B
Mic
19
19
26
18
10
1
9
Voice Detect
26
18
10
1
9
Voice Detect
Digital PTT
Digital PTT
Mic
GND
Digital ↔ Digital
1) Ground wire
To connect PIN2 of digital repeater 1 and that of digital repeater 2.
2) Activation of repeater transmission
To connect PIN3 of digital repeater 1 and PIN16 of digital repeater 2.
To connect PIN16 of digital repeater 1 and PIN3 of digital repeater 2.
3) Digital audio output
To connect PIN24 or PIN25 of digital repeater 1 and PIN7 of digital repeater 2.
To connect PIN7 of digital repeater 1 and PIN24 or PIN25 of digital repeater 2.
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Part III How to Realize Back to Back?
Key Configurations in Programming(Mobile Radio)
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Part III How to Realize Back to Back?
Key Configurations in Programming(Repeater)
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Part IV FAQ
1 How many mobile radios/repeaters can be connected in the back-toback way?
To ensure an optimal performance, only two mobile radios/repeaters
are supported at the present stage.
2 Can the communication go with the same frequency?
It is recommended to use different frequencies to avoid signal
interference.
3 Is there any suggestion for configuring the frequency?
To ensure communication performance, it is suggested to maintain the
frequency space at 100KHz or more.
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Part IV FAQ
4 Is there any requirement on the bandwidth?
The bandwidth of two repeaters can be different. For example, the
bandwidth of digital repeater is 12.5 KHz, and the bandwidth of
analog repeater is 12.5 KHz, 20 KHz, or 25 KHz. The bandwidth
difference does not affect the back-to-back performance.
5 How long is the accessory pin cable?
It is recommended to keep the cable length within 1M.
6 Why does the prompt “Service Rejected” appear frequently?
The reason is that the repeater is transmitting via the external Mic
PTT, making it unable to handle other call requests. You can try it
again later.
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Part IV FAQ
7 How to deal with back-to-back function failure?
When the back-to-back function does not work, take the steps below:
1) Check whether the accessory pin cable is connected properly. If
not, reconnect it;
2) Restart the repeater;
3) If the above steps do not help, please contact your dealer.
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Back to Back Cable
Material Code
Description
4251200000500
Wire kit repeater accessory connector adapter cable PU90A OD:4.0mm DB26 L1200mm (RoHS)
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THANKS
Please call or email Hytera Global Customer Service Center, if you have any
question about Hytera Product.
Service Direct Line:
+86-755-86137081
Email:
overseas.service@hytera.com
Website:
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