Emergency Dispatch System

Rationale: NENA standard 56-005 specifies 90 percent at 15 seconds and 95 percent at 20 seconds answer-time targets for E911 PSAPs. Exceeding these thresholds directly correlates with increased mortality in cardiac arrest and trauma cases where every second of delayed response reduces survival probability by approximately 10 percent.

Rationale: FCC wireless E911 mandates require location accuracy for emergency calls. Without accurate caller location, dispatchers must rely on verbal information that may be unreliable when callers are distressed, unfamiliar with the area, or unconscious. Incorrect unit dispatch wastes critical response time and can be fatal in time-sensitive emergencies.

Rationale: Field units arriving without incident context face elevated risk and delayed effective response. Pre-arrival information on hazmat, weapons, building layout enables en-route tactical planning and appropriate resource staging, directly improving both responder safety and victim outcomes.

Rationale: Emergency dispatch is life-safety critical with no acceptable downtime. 99.999 percent availability aligns with NENA NG911 core service reliability standards. Complete dispatch failure during a mass-casualty event could result in preventable deaths across the served jurisdiction, typically covering 100,000+ residents.

Rationale: State and federal regulations mandate retention of 911 call recordings as public safety records and potential legal evidence. Failure to record or retain creates legal liability for the PSAP, undermines post-incident review and quality assurance, and may violate discovery obligations in litigation arising from emergency response.

Rationale: Without real-time operational visibility, supervisors cannot detect queue overflows, unbalanced dispatcher workloads, or degraded response times until callers complain or incidents escalate. Dynamic resource management requires continuous metrics to trigger overtime callbacks, mutual aid activation, or position reassignment.

Rationale: PSAPs must handle calls outside their jurisdiction and coordinate mutual aid during large-scale incidents. NENA i3 standards require location and context transfer between PSAPs. Without seamless transfer, callers must repeat information to receiving dispatchers, wasting time and risking transcription errors during high-stress situations.

Rationale: The Americans with Disabilities Act and FCC mandate that 911 services be accessible to persons who are deaf, hard-of-hearing, or speech-impaired. Text-to-911 and telematics channels are legally required access methods. Telematics automatic crash notification provides critical data for unresponsive vehicle occupants who cannot place voice calls.

Rationale: FCC E911 Phase II mandates 50-metre accuracy for 67 percent of wireless calls. Wireline ALI provides street-address-level accuracy. The 10-second time constraint ensures location is available before the call-taker finishes initial questioning.

Rationale: FCC E911 Phase II mandates 50-metre accuracy for 67 percent of wireless calls. Wireline ALI provides street-address-level accuracy. The 10-second time constraint ensures location is available before the call-taker finishes initial questioning.

Rationale: Emergency dispatch is a 24/7 life-safety service that cannot tolerate scheduled downtime. PSAP administrators need the ability to apply security patches and perform hardware maintenance without interrupting dispatch operations. Maintaining voice call and radio capability during maintenance ensures the public can still reach 911 and dispatchers can still communicate with field units.

Rationale: Duplicate of STK-NEEDS-011 — created during validation session. This requirement restates the maintainability need for zero-downtime updates to the emergency dispatch system, ensuring 24/7 service continuity during maintenance windows.

Rationale: Derived from STK-NEEDS-001. A metropolitan PSAP serving 500,000+ population may receive 3,000+ calls per day with peak concurrency during severe weather or mass events. 150 concurrent calls represents a 3x peak margin over typical busy-hour loads of 50 concurrent calls, ensuring the system does not become a bottleneck during surge events.

Rationale: Derived from STK-NEEDS-001. The 2-second end-to-end target allocates processing budget across ESInet gateway, ACD routing, ANI/ALI lookup, and workstation presentation. Exceeding 2 seconds adds directly to the call answer time measured by NENA standards, and each additional second of silence causes callers to hang up and redial, creating phantom load on the system.

Rationale: Derived from STK-NEEDS-002. The FCC E911 location accuracy benchmark requires 50-metre horizontal accuracy for 80 percent of wireless calls. This is the minimum needed to dispatch to the correct building in urban environments. Without this accuracy, responders may search the wrong location while the caller is in distress at a different address.

Rationale: Derived from STK-NEEDS-003. The 5-second dispatch delivery target ensures field units receive assignment data while still en route from their station. Longer delivery times mean units arrive at intersections without knowing which direction to proceed, or arrive on scene without hazard awareness. 5 seconds allows the MDT to display and the crew to acknowledge before reaching the response zone.

Rationale: Derived from STK-NEEDS-004. 99.999 percent availability permits 5.26 minutes annual downtime. The 30-second failover window ensures active calls are not dropped during component failure. Loss of in-progress incident data during failover could cause dispatched units to lose their assignment or duplicate dispatches to be generated, creating confusion during active emergencies.

Rationale: Derived from STK-NEEDS-005. Dual-redundant recording eliminates single-point recording failure which would create unrecoverable evidence gaps. 5-year retention satisfies the most stringent state statutes. Chain-of-custody metadata is required for recordings to be admissible as evidence in criminal proceedings and civil liability cases arising from emergency response.

Rationale: Derived from STK-NEEDS-006. The 5-second refresh interval provides near-real-time situational awareness without imposing excessive query load on the CAD database. Supervisors use this dashboard to detect queue depth spikes within 10 seconds of onset, enabling immediate intervention such as activating overflow routing or recalling off-duty dispatchers.

Rationale: Derived from STK-NEEDS-007. NENA i3 SIP REFER is the standard inter-PSAP transfer mechanism. The 3-second transfer completion target ensures the receiving PSAP has caller context before audio connects, preventing the caller from having to repeat their emergency while the receiving dispatcher has no information. Location and callback number transfer eliminates manual re-entry errors.

Rationale: Derived from STK-NEEDS-008. Equal priority queuing for text sessions ensures ADA-mandated equitable access. Text callers in active-shooter or domestic-violence situations cannot use voice and must not be relegated to a secondary queue. Unified workflow means dispatchers handle text with the same incident-creation and location-display tools as voice, reducing training burden and error rates.

Rationale: Derived from STK-NEEDS-004. CJIS Security Policy v5.9 is mandatory for any system accessing criminal justice information. PSAPs routinely query NCIC and state criminal databases during dispatch. Failure to implement CJIS controls results in decertification, loss of database access, and potential federal enforcement action. Network segmentation prevents lateral movement from compromised external-facing systems into the PSAP core.

Rationale: Cross-domain insight from air traffic control and naval CMS domains: complex real-time dispatch systems require training environments to certify new operators and validate procedure changes without risk to live operations. Isolation from production prevents synthetic training data from generating real dispatches, a failure mode documented in multiple PSAP incidents where test calls triggered real unit responses.

Rationale: NENA standards require PSAPs to maintain minimum dispatch capability during partial system failures. The 150 concurrent voice call floor reflects a medium-sized PSAP peak load. The 120-second call-to-dispatch ceiling for Priority Emergency ensures life-threatening incidents still receive timely response even when CAD, GIS, or records subsystems are unavailable and dispatchers fall back to manual procedures.

Rationale: Geographic diversity of backup PSAPs protects against regional disasters (earthquakes, hurricanes, flooding) that could disable the primary site. The 25-mile minimum separation is derived from FEMA regional disaster impact zones. The 60-second failover target ensures callers experience minimal disruption during site transition. 100 percent capacity at the backup site prevents capacity degradation during extended primary outages.

Rationale: Derives from STK-NEEDS-011 maintainability need. Rolling updates to individual subsystems allow patching security vulnerabilities and deploying bug fixes without system-wide downtime. The 30-minute window per subsystem bounds maintenance impact and enables scheduling updates across subsystems sequentially during low-traffic periods while keeping all other subsystems operational.