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DMR Application-Back to Back

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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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The “back-to-back” is a system solution on accessory pins. It is used to achieve cross-band communication among analog and digital radios.

Definition

Part I What’s Back to Back?

Analog Radio DMR Digital Radio

Back to Back

UHF VHF

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Work Principle(Mobile Radio)

Part II How Back to Back Works?

MR 1Tx=Rx=f1

MR 2Tx=Rx=f2

R1

R2

R3

R4

R5

R6

Tx=Rx=f1

Tx=Rx=f1 Tx=Rx=f2

Tx=Rx=f2

Tx=Rx=f2Tx=Rx=f1

Pin PinEnable PTT

Audio Output

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Work Principle(Repeater)

Part II How Back to Back Works?

Repeater 1Tx=f2 Rx=f1

Repeater 2Tx=f4 Rx=f3

R1

R2

R3

R4

R5

R6

Tx=f1Rx=f2

Tx=f1Rx=f2

Tx=f3Rx=f4

Tx=f3Rx=f4

Tx=f3Rx=f4

Tx=f1Rx=f2

Pin PinEnable PTT

Audio Output

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Accessory Pin(Mobile Radio)

Part II How Back to Back Works?

The mobile radios can be connected in a back-to-back manner as below

10

19

1 9

18

26

10

19

1 9

18

26

MR 1 MR 2

GND

Audio Output

Speaker Open Detect

Mic

Ext Mic PTT

Speaker Open DetectMic Audio Output

Ext Mic PTT

1) Ground wireTo connect Pin2 of mobile radio1 and that of mobile radio 2.2) Activation of mobile radio transmissionTo 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 outputTo 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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Accessory Pin(Repeater)

Part II How Back to Back Works?

Analog ↔ Digital

10

19

1 9

18

26

10

19

1 9

18

26

Analog Repeater Digital Repeater

GND

Slot-A Slot-B

Digital PTTAudio Output

Carrier DetectMicAnalog PTT

Mic

Voice Detect

1) Ground wireTo connect PIN2 of analog repeater and that of digital repeater. 2) Activation of digital repeater transmissionTo connect PIN3 of analog repeater and PIN16 of digital repeater.3) Analog audio outputTo connect PIN8 of analog repeater and PIN7 of digital repeater.4) Activation of analog repeater transmissionTo connect PIN16 of analog repeater and PIN3 of digital repeater.5) Digital audio outputTo connect PIN7 of analog repeater and PIN24 or PIN25 of digital repeater.

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Accessory Pin(Repeater)

Part II How Back to Back Works?

Analog ↔ Analog

10

19

1 9

18

26

10

19

1 9

18

26

Analog Repeater 1 Analog Repeater 2

GND

Analog PTTAudio OutputCarrier Detect

Mic

Analog PTT

Carrier DetectMic Audio Output

1) Ground wireTo connect PIN2 of analog repeater 1 and that of analog repeater 2.2) Activation of repeater transmissionTo 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 outputTo 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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Accessory Pin(Repeater)

Part II How Back to Back Works?

Digital ↔ Digital

10

19

1 9

18

26

10

19

1 9

18

26

Digital Repeater 1 Digital Repeater 2

GND

Slot-A Slot-B

Digital PTTVoice DetectMic

Mic

Voice DetectDigital PTT

Slot-A

Slot-B

1) Ground wireTo connect PIN2 of digital repeater 1 and that of digital repeater 2.2) Activation of repeater transmissionTo 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 outputTo 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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Key Configurations in Programming(Repeater)

Part III How to Realize Back to Back?

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Part IV FAQ

1 How many mobile radios/repeaters can be connected in the back-to-back 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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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.

Part IV FAQ

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Material Code Description

4251200000500 Wire kit repeater accessory connector adapter cable PU-90A OD:4.0mm DB26 L1200mm (RoHS)

Back to Back Cable

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question about Hytera Product.

Service Direct Line: +86-755-86137081

Email: overseas.service@hytera.com

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