Redundant Repeater Setup

By using the Major Alarm output and FCC Type 2 Monitor input together, it is possible to setup redundant repeaters - so that if the main repeater fails, the standby repeater can take over. Both repeaters are programmed 100% the same except for the below.

One operates as the main repeater and the other one as a standby repeater. For
the main repeater, one GPIO pin is configured for Major Alarm reporting with an active high polarity. For the standby repeater, one of its GPIO pins is configured as FCC Type 2 Monitor control input and its polarity is the opposite of the main repeater’s alarm: active low.

Accessory GPIO configuration (Main)
Accessory GPIO configuration (Standby)
When the main repeater’s alarm pin becomes active it deactivates the disabled pin and the standby repeater becomes enabled. If the repeater is a Master, there will be a short outage on the wide area network while the Peers re-register with the standby Master.
Interface cable connection


The above cable is custom-made. The connectors are available from Motorola PMLN5072A. Pin positions are shown below. Remember that a common Ground is required and this can be found on pin 16.

PMLN5072 pin numbering
Optionally, an antenna switch can be used however some antenna switches require a significant amount of current to energise the RF relay within – in such cases it is necessary to install a driver circuit between the repeater output and antenna switch trigger input.

If repeaters are operating in IP site Connect or Capacity Plus mode, they must both have existing IP network connections and be communicating with the Master. Since they are both on the same network, they must have different IP Addresses. Although the system will not send voice to a disabled repeater, it will require link management and therefore a small amount of bandwidth.
A redundant repeater connected to the IP Site Connect system or Capacity Plus system counts in the total number of supported peers.

It is also important to note that when setting up the Master repeater of an IP Site Connect; Capacity Plus or Linked Capacity Plus system into a redundant configuration, the network link must also be switched with external hardware similar to that of the antenna switch. In this case, the IP Address of both the Primary and the Standby repeaters must be the same since all the Peers communicate with it using this IP address. As they have the same IP Address, they cannot be connected to the network at the same time.

Some Routers are able to support automatic switchover to a standby device (repeater) when a device (main repeater) stops sending or receiving packets. 

This also means that the standby repeater cannot be contacted via a network RDAC application while not in the primary repeater role since it is not connected to the network. Because the two devices have the same IP address but different MAC addresses, Peers may not be able to contact the Master repeater until the router and repeater ARP tables are updated. Depending on router configuration this could take up to 15 to 20 minutes. It is recommended to consult the Network Administrator for details on setting the ARP interval within the customer’s network.

(Source: MOTOTRBO System Planner 68007024085 Revision J)

13 comments:

  1. what about the TRBOnet dispatcher, it can it sense the swapping ?

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    Replies
    1. Yes, but TRBONET Watch, not Enterprise or Plus.

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  2. What is the function of the "Backup Repeater Connected" tick box under General Settings in the DR3000 and how should it be used?
    The help documentation relating to this option describes what you have covered in this article. Doesn't this make the "Backup Repeater Connected" tick box pointless?
    I found this article useful because the "Backup Repeater Connected" option doesn't seem to affect the accessory outputs, no matter what i set the GPIOs to.

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    1. My understanding is that ticking this will affect the way in which alarm conditions are reported in RDAC (or whichever System Monitoring application is used https://bitly.com/bundles/cwh050/a). If this is ticked and there is a PA fail on the standby unit, for example, the alarm will be reported as minor instead of major. The main unit is still running and so the site isn't down. If the same fault occurs on the main unit, the alarm will be reported as major requiring immediate attention.

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  3. Hi I'm James. Thank you for this is very informative. I have some inquiries, what will happen if the Ethernet link between the master repeater and the router fails, will the master trigger an alarm to activate the standby or the system monitoring application will do the alarm trigger to activate the standby?

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    1. In the above case, the repeater itself will trigger the standby repeater to come "online". It works well with Peer repeaters but the Master requires some additional switching since a "knocked-down" repeater will still keep its ethernet adapter up and so there would be some conflicts. At least one Motorola Distribution Partner in EMEA has solved this via a custom-made solution (single board computer controlling two ethernet switches).

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  4. Hi Wayne,

    Who makes the Antenna switches you refer to interfacing the Primary and Secondary repeaters to the external antenna, whilst having a connection to the repeaters GPIO Pins?
    Thanks..

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  5. Hi Wayne,

    Who makes the Antenna switches you refer to interfacing the Primary and Secondary repeaters to the external antenna, whilst having a connection to the repeaters GPIO Pins?
    Thanks..

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    Replies
    1. I found one from Jotron which is intended for aviation use. Otherwise this can be easily manufactured if you dont find exactly what you need.

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    2. Hi Wayne, if you refer to section 2.10.4 of the MotoTRBO System Feature Overview document, the diagram shows connections from the TX and RX ports of both repeaters in to the Antenna switch, and in between that it shows a connection from the GPIO pins of the two repeaters to the antenna switch as well. Where does the line that comes out from the GPIO pins connect on the Jotron switch you mentioned?

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    3. What you may be referring to is an MTR3000 operating in base station mode: here the repeater works as a normal transceiver and not a repeater. The relay (a Motorola part) switches the antenna between transmit and receive on PTT. There is a dedicated output on the MTR to drive the relay.

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