Info: Features - Stun, Unstun, Radio Check, Remote Monitor, Call alert

[emsgeorge]

Stun and Unstun:

The Radio Disable feature can be used to stop any inappropriate use of a radio, or to prevent a
stolen radio from functioning. In MOTOTRBO systems, Radio Disable is configured in the portable
and mobile radios with the CPS. To allow a radio to use this function, it must be enabled in the
CPS “Menu” settings. To permit (or prevent) a radio from receiving and responding to this
command, go to the “Signaling Systems” settings in the CPS.

When disabled, the radio's display blanks and the radio is no longer able to make or receive calls.
The radio can still be turned on and off; this indicates that the radio has not failed, but is disabled.
Once disabled, a radio can also be enabled via the CPS. All radios are configured to accept Inhibit
commands by default, but this can be disabled via the CPS.

For over-the-air radio enable signaling to be successful, the target radio must be turned on and be
within coverage of the site it was disabled at. This is important since a disabled radio locks onto
the site or channel on which it was disabled, even after a power cycle. To receive an enable
command over-the-air, the radio also has to be within coverage of the site where the disabling
occurred. This may also be accomplished by communicating with the radio on the talkaround
frequency of the site in which it was disabled.

Remote Monitor:

The Remote Monitor feature allows a remote user to activate a target radio’s microphone and
transmitter for a period of time. A call is silently set up on the target radio, and its PTT is controlled
remotely without any indications given to the end user. The duration that the target radio transmits
after receiving a Remote Monitor command is set in the target radio through the CPS. When
receiving the Remote Monitor command, the target radio initiates a Private Call back to the
originator of the Remote Monitor command.

This feature is used to ascertain the situation of a target radio which is powered-on, but is
unresponsive. This is beneficial in a number of situations including:

• theft,
• incapacity of the radio user, or
• allowing the initiator of an Emergency Call to communicate hands-free in an emergency
situation.

In MOTOTRBO systems, Remote Monitor is configured in portable and mobile radio CPS. To allow
a radio to use this function, it must be enabled in the CPS “Menu” settings. To permit (or prevent) a
radio from receiving and responding to this command, go to the “Signaling Systems” settings in the
CPS. When a radio is configured to decode the remote monitor command, the duration that the
target radio transmits after receiving a Remote Monitor command is also set in the CPS “Signaling
Systems” settings of the target radio.

The Remote Monitor feature may be activated on a disabled radio. Remote Monitor could also be
programmed to be activated on radios that are in emergency mode only.

Radio Check

The Radio Check feature checks if a radio is active in a system without notifying the user of the
target radio. Besides the Busy LED, there is no other audible or visual indication on the checked
radio. The receiving radio automatically and silently responds with an acknowledgement to the
initiating radio.

This feature is used to discreetly determine if a target radio is available. For example, if a radio
user is non-responsive, Radio Check could be used to determine if the target radio is switched on
and monitoring the channel. If the target radio responds with an acknowledgement, the initiator
could then take additional action such as using the Remote Monitor command to activate the
target radio’s PTT.

In MOTOTRBO systems, Radio Check is configured in portable and mobile radio CPS. To allow a
radio to use this function, it must be enabled in the CPS “Menu” settings. All MOTOTRBO radios
will receive and respond to a Radio Check, i.e. this feature cannot be turned off in the CPS

Call Alert:

The Call Alert feature allows a radio user to essentially page another user. When a radio receives
a Call Alert, a persistent audible and visual alert is presented to the user. The initiator of the Call
Alert is also displayed. If a user is away from his radio at the time of the reception, the alert
remains until the user clears the Call Alert screen. If the user presses the PTT while the Call Alert
screen is active, he starts an Individual Call to the originator of the Call Alert. For in-vehicle
applications, this is often used in conjunction with the Horn and Lights option. When a user is away
from his vehicle, a Call Alert can initiate the vehicle’s horn and lights to sound and flash, which
notifies the user to return to the vehicle and call the originator.

In MOTOTRBO systems, Call Alert is configured in portable and mobile radio CPS. To allow a
radio to use this function, it must be enabled in the CPS “Menu” settings. All MOTOTRBO radios
will receive and respond to a Call Alert (i.e. you cannot disable this feature by using the CPS).

[goodwija]

Really useful info

Any chance of describing how the scan feature works e.g. does it only work on digital or FM, does it only work for channels in a single zone or can you collect channels from many zones etc

Thanks

[JtB]

I hope the following makes sense.

If Auto Scan is enabled for a channel, then the radio starts scanning as soon as that channel is selected by the user, otherwise if Auto Scan is disabled then scan can be started / stopped via a programmable button. While a radio is scanning it is continually sampling the Scan Members (channels) contained in the Scan List associated with that channel. A single Scan List can contain up to 16 Scan Members and you can define a maximum of 250 Scan Lists for a radio.

While a radio is sampling Scan Members in a Scan List it is looking for transmissions (voice or signaling) addressed to itself using any of the following addresses:
1) The radio's individual address
2) One of the radio's group addresses*
3) The "All Call" address

* The group addresses for a given channel are defined by the Group Members (group addresses) contained in the Receiver (Rx) Group List associated with that channel. So while a radio is sampling a particular channel in the Scan List, it is looking for incoming group calls contained in the Rx Group List associated with the channel it is sampling.

Scanning is only supported for conventional channels, so it does not apply to Capacity Plus personalities. A Scan List may contain any type of conventional channel, so it may contain a mixture of one or more types of the following:
1) Analogue direct channels
2) Analogue repeater channels
3) Digital direct channels
4) Digital single site repeater channels
5) Digital IP Site Connect repeater channels**

** An IP Site Connect Channel can not select both the Roam and Scan options together. So it is not possible for a radio to roam to a given site of a wide area channel and then to scan channels at that site.

It makes no difference which zones the above channels in the Scan List are taken from, so a Scan List may contain a mixture of conventional channels taken from multiple zones (note: zones are just a convenient way of partitioning channels into blocks of 16, and this is necessary because the channel selector on a portable has only has 16 positions).

While a radio is sampling a given Scan member (channel), if it detects a transmission (voice or signaling) addressed to itself, then the radio stops scanning and switches to that channel. The radio then remains on that channel until the call ends, in other words until all activity of interest has ceased on that channel for a period of time defined by the radio "Scan Hang Timer" (or until a higher priority call is detected).

For direct (i.e. non-repeater) channels, the radio "Scan Hang Timer" and the radio "Call Hang Timer" start together when the activity of interest ceases. For analogue repeater channels, the radio "Scan Hang Timer" starts when the repeater "Call Hang Timer" expires. For digital repeater channels, the radio "Scan Hang Timer" and repeater "Call Hang Timer" start together when the activity on the repeater inbound channel ceases. To ensure that the radio does not resume scanning before the call has ended, you need to configure the radio "Scan Hang Timer" to be longer than any of the radio or repeater "Call Hang Timers".

It is possible to assign priorities to Scan members in a Scan List; one channel can be assigned Priority 1, one channel can be assigned Priority 2 and all other channels are Non-Priority. The priority levels affect the order in which the radio samples Scan Members in a Scan List such that higher priority channels get sampled more frequently. Additionally, the currently selected channel (as indicated by the position of the channel rotary) is sampled more frequently than all other channels.

As already mentioned, when a radio detects an incoming group call on a given channel, the radio stops scanning and switches to that channel for the duration of the call. However, the radio continues to periodically sample higher priority channels in the Scan List and if a relevant incoming call is detected on a higher priority channel, then the radio will switch to the higher priority channel immediately without waiting for the current call to end.

The problem with this however is that while a radio is sampling a higher priority channel it is away from the current call and this introduces audio holes. A way of mitigating this problem is to select the "Channel Marking" option which minimizes the amount of time the radio is away from the current channel sampling higher priority channels. This option works by allowing the radio not to fully sample a priority channel every time once it has determined a call to be in progress (on a higher priority channel) which is not of interest. Fully decoding the address of a call in progress takes a long time, however if the radio knows a call is in progress which is not of interest on a higher priority channel, then it samples only a few address bits just to reassure itself that that the same call is still in progress. By doing this the radio is able to get back to its own call faster and hence minimize the audio holes.

As mentioned above, while a radio is sampling Scan members in a Scan List it is looking for transmissions (voice or signaling) addressed to itself. If the Scan List contains lots of channels, then the radio most likely will not be sampling a given channel at the precise moment when a call commences on that channel. For group calls this is not so much of a problem because the radio will still enter the group call by late entry when the radio finally gets round to sampling that channel. For signaling (e.g. remote monitor) and individual calls however, the radio needs to be sampling the right channel at the precise moment when the call commences. To achieve this you need to configure all radios in the system to transmit preamble when they setup a new call. This preamble gives scanning radios the opportunity to arrive on the right channel before the call itself commences. Please be aware however that scanning (even with preamble) does not work for emergency calls or data. Both these types of call will only be received on the currently selected channel (as indicated by the position of the channel rotary) irrespective of whether scan is enabled or disabled.

There's lots more to scan, but I shall leave it there for now.

[JtB]

if the radio knows a call is in progress which is not of interest on a higher priority channel, then it samples only a few address bits just to reassure itself that that the same call is still in progress

For readability purposes I oversimplified this a bit. For those who are familiar with the ETSI DMR standard, what the radio actually does is look at a compressed (8 bit) representation of the full (24 bit) destination address known as the "Hashed address" which is carried by the Short Link Control in the CACH (Common Announcement Channel). This compressed (Hashed) address is transmitted more regularly than the full destination address and hence allows the radio to get back to its current call faster.

[JtB]

There's lots more to scan, but I shall leave it there for now.

The other thing I wanted to mention about scan relates to Tx Designated Channels and Talkback.

If the user presses the PTT while the radio is scanning, the radio will (depending on its configuration) transmit on one of the following channels:
1) The Selected channel - this is the typical configuration.
2) A specified conventional channel.
3) The Last Active channel*** (i.e. the most recent channel on which the radio stopped scanning as a result of finding “Activity of Interest”).

If the user presses the PTT after the radio has stopped scanning as a result of finding “Activity of Interest”, the radio will (depending on its configuration) transmit on one of the following channels:
1) The Active Channel (i.e. the current channel on which the radio stopped scanning as a result of finding “Activity of Interest”) – this is the typical configuration.
2) The selected channel.
3) A specified conventional channel.

***  The radio only remembers the Last Active channel and NOT the Last Active group, therefore this configuration results in a transmission to the TX Contact Name associated with the Last Active channel (which is not necessarily the Last Active group). To avoid confusion, it is recommended that this configuration is only used if there is a single group in the RX Group List for each channel and this single group corresponds to the channel’s TX Contact Name.

While a radio is sampling a given Scan member (channel), if it detects a transmission (voice or signaling) addressed to itself, then the radio stops scanning and switches to that channel. The radio then remains on that channel until the call ends, in other words until all activity of interest has ceased on that channel for a period of time defined by the radio "Scan Hang Timer" (or until a higher priority call is detected).

For direct (i.e. non-repeater) channels, the radio "Scan Hang Timer" and the radio "Call Hang Timer" start together when the activity of interest ceases. For analogue repeater channels, the radio "Scan Hang Timer" starts when the repeater "Call Hang Timer" expires. For digital repeater channels, the radio "Scan Hang Timer" and repeater "Call Hang Timer" start together when the activity on the repeater inbound channel ceases. To ensure that the radio does not resume scanning before the call has ended, you need to configure the radio "Scan Hang Timer" to be longer than any of the radio or repeater "Call Hang Timers".

Actually, the above describes the original MOTOTRBO implementation, whereas more recent MOTOTRBO releases provide a more logical implementation as follows:

While sampling a given channel, if “Activity of Interest” is found the radio stops scanning and switches to that channel. The radio then remains on that channel until all “Activity of Interest” has ceased for a period of time defined by the “Call Hang Timer” (if applicable) plus the radio “Scan Hang Timer”. Once the “Scan Hang Timer” expires then the radio resumes scanning again.

For digital and analogue repeater channels:
1) On termination of a radio transmission, the repeater starts its Call Hang Timer running.
2) On expiry of the Repeater Call Hang Timer, receiving radios start their Scan Hang Timers running.

For digital direct radio channels:
1) On termination of a radio transmission, receiving radios start their (Talkaround) Call Hang Timers running.
2) On termination of a (Talkaround) Call Hang Timer, a receiving radio starts its Scan Hang Timer running.

For analogue direct radio channels:
1) Call Hang Timers do not apply here, so on termination of a radio transmission, receiving radios start their Scan Hang Timers running immediately.

[JtB]

if the radio knows a call is in progress which is not of interest on a higher priority channel, then it samples only a few address bits just to reassure itself that that the same call is still in progress

For readability purposes I oversimplified this a bit. For those who are familiar with the ETSI DMR standard, what the radio actually does is look at a compressed (8 bit) representation of the full (24 bit) destination address known as the "Hashed address" which is carried by the Short Link Control in the CACH (Common Announcement Channel). This compressed (Hashed) address is transmitted more regularly than the full destination address and hence allows the radio to get back to its current call faster.

Please ignore the above explanation (it's a long time since I worked with this and I got a bit muddled). The radio actually uses the "Hashed address" to minimise the audio holes if it's currently unmuted to a lower priority voice call and the higher priority channel is the other timeslot on the same repeater.

For "Channel Marking" the radio assumes that if the activity on the higher priority channel has already been validated as not of interest, then there is no need to fully review it at every scan interval. For a partial review the radio only verifies that the activity on the higher priority channel is of the same type as the activity which was previously identified as not of interest. If this is the case then the radio assumes the current activity on the higher priority channel is the same activity which was previously identified as not of interest. By verifying just the type of activity, the radio is able to get back to the current call much faster. This assumption is made for a pre-determined number of times, after which the activity on the higher priority channel is fully reviewed again.