Emergency Call Pillar Product

Overview

An emergency call pillar is a street-furniture-mounted two-way voice system connecting the public to emergency dispatch. Common in universities, parks, parking lots, and transit centers, these pillars provide instant communication to security or 911 operators without requiring a personal cell phone. The user approaches the pillar, presses the call button, hears a voice response from dispatch, and describes their emergency. The dispatcher can simultaneously see video from the pillar's camera (if equipped) and pinpoint the exact location via GPS.

The Speakerphone Unit handles audio, incorporating high-gain microphone and speaker for operation outdoors where wind and traffic noise are present. The Strobe Light Module provides visual feedback and marks the pillar's location to responders. An optional Camera Module (Optional) adds situational awareness, recording video and audio of the incident for later review.

Connectivity is provided via the Network Communication, which may use GSM (cellular), Ethernet (if in-building), or SIP VoIP (if on a campus or corporate network). The Master Controller is the processing core, managing audio routing, call setup, and light/siren sequencing.

How it works

The user presses the call button on the Pillar Housing. The Master Controller receives the signal and initiates a call to a pre-programmed emergency dispatch center number via the Network Communication. If cellular (GSM), the GSM/LTE Modem establishes a circuit-switched voice call. If VoIP, the VoIP Module sends a SIP INVITE to the dispatch server, establishing a real-time audio session.

The Speakerphone Unit is now connected to the dispatcher. The Speakerphone Microphone captures the caller's voice through analog Audio Codec (an ADC / DAC pair), and the Echo Canceller suppresses feedback that might occur if the Speaker and microphone are too close. The caller hears the dispatcher's voice at a comfortable level through the speaker, and the dispatcher hears the caller clearly, even with traffic noise.

Simultaneously, if equipped, the Camera Module (Optional) activates. The CMOS Image Sensor at the back of the lens captures the scene, and the Camera Processor compresses video into H.264 format at 30 fps, 2 Mbps bandwidth. This stream is transmitted to the dispatch center via the same network connection (GSM, Ethernet, or VoIP session), allowing the dispatcher to see the caller's surroundings—are they injured, is there a weapon, are there bystanders?

The Strobe Light Module flashes at 1–2 Hz, a standard emergency strobe pattern. If a siren is integrated, the Relay Control Board energizes the siren solenoid, producing a loud tone that alerts people in the vicinity and draws attention to the emergency location.

The dispatcher navigates a computer system showing the pillar's GPS location (derived from the pillar's cellular network registration or from a emergency-call-pillar-gps-receiver built into some models). The dispatcher can also trigger text-to-speech messages back through the pillar, saying "Help is on the way" in any configured language.

Power is the challenge in outdoor unattended equipment. The pillar is likely fed by a mains 120 V AC line run underground, but a Power System with a Backup Battery ensures that the pillar remains operational during a power outage—when emergencies are often most critical. The backup is typically a 12 V SLA (sealed lead-acid) battery, rated 20–50 Ah, providing 2–4 hours of talk time. The Battery Charger is a constant-voltage or trickle charger that keeps the battery topped off during normal operation.

Audio quality is critical and challenging in outdoor environments. The Echo Canceller uses a DSP to model the acoustic environment and subtract the speaker's output from the microphone signal in real time. Without it, the dispatcher would hear their own voice echoing back with a 50–100 ms delay, making conversation unintelligible. The Audio Board includes the conditioning circuitry: line amplifiers, a codec (ADC/DAC), and digital signal processing.

Calls are typically routed via SIP to a VoIP dispatch center, or via GSM SMS / voice to a 911 center. The Master Controller manages the call state: idle (awaiting a button press), ringing (the call is connecting), active (audio flowing), and post-call logging. Call duration, timestamp, and caller location are all recorded for documentation.

Maintenance is annual: inspection of the door seal and housing for corrosion, testing the strobe and siren, and replacing the battery if it fails a load test. The microphone and speaker are replaced every 5–10 years due to corrosion and mechanical wear. The entire pillar has a lifespan of 15–20 years.