¶ Talkgroup and Routing Behaviour
IPSC3 keeps group-call routing, private-call routing, scan mode, and DMR data
handling separate. This reduces unexpected talkgroup drag-back and makes the
RF user experience more predictable.
| Mode |
Behaviour |
| static | Always eligible for delivery according to policy and endpoint state. |
| dynamic | Requires the endpoint to camp onto the talkgroup by keying it. |
| listen only | Accepts trunk inbound traffic but rejects local RF transmit attempts with voice feedback. |
- Dynamic talkgroups use a per-talkgroup camp timeout.
- A repeater or hotspot becomes camped on a dynamic talkgroup when a user keys that talkgroup.
- The first RF stream from an endpoint that is not already camped on that talkgroup and timeslot is treated as a local camp-establishment stream, regardless of how long the user holds PTT. It is not transmitted to other endpoints or trunks.
- After the user releases PTT, an idle talkgroup returns the local voice message
<talkgroup number> now linked.
- The link message carries one second of continuous in-band AMBE silence before speech. This keeps the endpoint keyed while strict subscriber radios open and prevents the first syllable from being clipped.
- If the talkgroup is already active elsewhere, IPSC3 does not interrupt it with the link message. The endpoint joins the remaining call with fresh late-entry signalling so strict DMR radios can decode it.
- Once camped, later transmissions on the same talkgroup and timeslot route normally.
- This establishment rule applies to RF endpoints, including MMDVM hotspots/repeaters, Motorola IPSC repeaters, and Hytera repeaters. Trunk and POC ingress are not treated as camp requests.
- Keying a different talkgroup on the same endpoint clears or replaces the previous camp.
400 cancels a camped dynamic talkgroup on repeaters and hotspots.- Private calls also clear scan or dynamic camp state on the calling endpoint.
- Static talkgroups do not expose a timeout in the same way as dynamic groups.
777 / TS1 is the scan trigger talkgroup. Keying it puts the
endpoint into scan mode. Active talkgroup traffic can then be translated onto
777 so the user can listen without manually selecting the active
talkgroup.
- Replying on
777 is translated back to the last active talkgroup.
- The user does not need to change to the active talkgroup to reply.
- Scan can be cancelled by keying another talkgroup or by keying
400.
777 is not treated as a normal live talkgroup on overview/status pages.
Hotspot operators can further control what scan mode delivers to their own
MMDVM hotspot by adding IPSC3 options in the hotspot options field:
ScanExclude=505,3801,3802 prevents the listed talkgroups from being sent to that hotspot while it is in scan mode.ScanInclude=3801,3802 does the reverse: only the listed talkgroups are allowed through while that hotspot is in scan mode.- If both options are present and a talkgroup appears in both lists,
ScanExclude wins.
- These options are per hotspot. They do not affect normal direct/camped talkgroup use, private calls, repeaters, trunks, or any other hotspot.
- Example:
ScanInclude=3801,3802;TalkerAlias=N
¶ Simplex and Duplex Hotspots
IPSC3 treats simplex and duplex hotspots differently because simplex hotspots
have only one effective RF path.
- Simplex is inferred when TX and RX frequencies are the same.
- Simplex hotspots use one effective slot.
- When a simplex hotspot is dynamically camped on a talkgroup, IPSC3 can suppress normal call-channel traffic for that session.
- This prevents the hotspot from being dragged back to the call channel while the user is using another dynamic group.
- Duplex hotspots behave more like two-slot repeaters.
Each trunk can have its own mapping list. A mapping defines a trunk-side
talkgroup and timeslot and the local IPSC3 talkgroup and timeslot it maps to.
- Inbound trunk traffic is rewritten from trunk TG/TS to local TG/TS.
- Outbound local traffic to that trunk is rewritten from local TG/TS back to trunk TG/TS.
- Mappings allow IPSC3 to connect networks that use different numbering or timeslot conventions.
- OpenBridge trunks are externally TS1-only, but local mapping can still translate talkgroups.
- bMaster+ trunks use the same mapping model while carrying Motorola/IPSC style group voice frames.
Each talkgroup can also have an allowlist of trunks that may carry it.
- If no allowlist rows exist for a talkgroup, legacy allow-all behaviour applies.
- Once a talkgroup has allowlist rows, only enabled rows are allowed.
- Inbound trunk traffic is checked after trunk mapping is translated into local TG/TS.
- Outbound traffic is checked before per-trunk outbound mapping is applied.
- bMaster+ trunks are opt-in only and require an explicit enabled checkbox for each talkgroup.
- This can keep selected talkgroups on selected trunks only.
¶ Private Calls and Roaming
Private calls use the RadioID destination and the current roaming/last-seen
radio state. This path is deliberately separate from group-call routing.
- Every received call can update the last-seen radio location where possible.
- The roaming dwell window is configured in system settings.
- If the destination radio is current, IPSC3 routes the private call to the last-seen endpoint.
- If the destination radio is missing or expired, IPSC3 sends a direct-call busy/unavailable voice response back to the caller.
- Parrot
9990 bypasses private-call routing so it can answer directly.
Listen-only talkgroups are useful when IPSC3 should receive traffic from a
trunk but should not allow local RF users to transmit back onto that
talkgroup.
- Trunk inbound traffic can still be delivered to local endpoints.
- Repeater or hotspot originated calls are rejected.
- The local caller receives voice busy feedback explaining the talkgroup is unavailable.