Intercom
Calls between cabs, cars and operator stations with per-project rules.
PASPA · SIP Module
PASPA public address and intercom with SIP Module
All train audio, managed from a single server
PASPA centralises intercom, public address, emergencies and recording on board. The SIP Module brings that intelligence to every audio terminal on the train.
PASPA orchestrates from the on-board server. The SIP Module is the embedded terminal. Together they form a complete railway audio communication system.
From scattered audio to a coherent system
Common situation
- Each audio device is configured separately, car by car.
- Call and PA priorities differ depending on the installed equipment.
- When trains are coupled, audio rules stop being consistent.
With PASPA
- Remote configuration and supervision of the whole audio fleet from a single point.
- Common call rules, priorities and emergencies across the whole consist.
- Ready for coupled trains with primary, secondary and hibernate roles.
On-train architecture
PASPA runs on the on-board server, handles telephony with Asterisk and talks over MQTT with the passenger information system and the TCMS. Each SIP terminal registers and receives its configuration from PASPA.
PASPA server
Asterisk (SIP)
MQTT
PIS / TCMS
SIP Module terminals
Key features
Passenger emergency
Priority handling of emergency intercoms and call-for-aid points.
Public address
Live or automatic announcements triggered from the passenger information system.
Cab calls
Direct communication between cabs, also in coupled trains.
Landside communication
Link with the control centre and radio gateway.
Mobile intercom
On-board staff communicate from mobile devices.
Recording
Recording of communications with configurable retention.
Driver interface
Web cab screen and back office tailored to each project.
PASPA technical specifications
| Area | Detail |
|---|---|
| Platform | Python 3.12+, async FastAPI, Pydantic v2 |
| Telephony | Asterisk 22.x, ARI + Stasis, dynamic PJSIP |
| Messaging | MQTT, integration with VDV-Web / PIS |
| API | REST documented with OpenAPI / Swagger |
| Topology | Train configuration: extensions, devices and dial plan |
| Roles | Primary / secondary / hibernate for coupled trains |
| Automatic volume | Adjustment to ambient noise towards the amplifiers |
| Deployment | On server (systemd, Ansible) or containers in the lab |
| Quality | Automated tests with target coverage ≥ 95% |
Integrated into the Joifilabs ecosystem
PASPA receives audio commands from the passenger information system, publishes broadcast status and shares the train configuration. Embedded terminals on Colway hardware complete the chain to every car.
Use cases
Passenger emergency
A passenger presses the intercom: PASPA prioritises the call, alerts the cab and records it.
Automatic announcements
The passenger information system triggers the next-stop announcement and PASPA broadcasts it in every car.
Operator call
The operator calls the cab from their panel with phonebook and handset.
SIP Module — Technical detail
One audio terminal for every role on the train
Embedded software on Colway hardware: SIP client, audio, inputs and outputs, peripherals and local API, centrally configured from PASPA.
Uniform terminal for emergency, cab, operator and PA.
Remote configuration and updates from PASPA.
Degraded mode on network failures.
Documented API for integration and field support.
Logical flow
- 1
PASPA sends the configuration to the module
- 2
The core applies it to each process
- 3
The SIP client registers with Asterisk
- 4
Events and alarms return to PASPA via webhooks and MQTT
Operating modes
| Mode | Device | Main use |
|---|---|---|
| PEI | Emergency intercom | Alarm and passenger–cab voice |
| CFA | Call for aid | Passenger assistance, horizontal or vertical layout |
| GOP | Operator panel | Phonebook, handset and operational calls |
| VI | Cab | Cab, PA selector and handset |
| AMP | PA amplifier | PA channels, automatic volume and streaming |
| AMP-V2 | Dual amplifier | Two synchronised SIP accounts |
| GATE | UIC audio gateway | Analogue UIC link, master / slave |
Interfaces
| Protocol | Purpose |
|---|---|
| SIP | Registration and calls with Asterisk (UDP/TCP/TLS) |
| HTTP | Local REST API for configuration and support |
| HTTPS | Secure REST API |
| MQTT | Automatic volume and events |
| RTP | Non-SIP PA where applicable |
| Webhooks | Events to PASPA (alarms, cab selector) |
States and recovery
IDLESIPSTREAMDEGRADEDANALOG
The module moves between idle, SIP call, streaming and degraded states. If the network fails, it keeps critical local functions and recovers automatically when the connection returns.
Configuration, audio and maintenance
Remote configuration
PASPA sends SIP account, MQTT, time, buttons, phonebook, webhooks and network supervision.
Audio and automatic volume
Echo and noise cancellation, gain control. Intercoms measure noise and amplifiers adjust the volume.
Security and updates
SIP over TLS, configurable API authentication (basic, key or mTLS), logs and remote updates orchestrated from PASPA.
Compatibility
Detects Colway hardware at boot and applies the right profile for each project.
SIP Module technical specifications
| Area | Detail |
|---|---|
| Platform | Python 3.11, multi-process architecture |
| SIP | PJSIP / PJSUA2 ≥ 2.17, UDP / TCP / TLS |
| Codecs | G.722, Opus, G.711, Speex, G.729, iLBC, GSM (configurable) |
| Audio | SGTL5000 codec; AEC, ANC, AGC and automatic volume |
| Peripherals | GPIO, buttons, handset, phonebook, PA selector |
| Deployment | Embedded Linux (Yocto), systemd service |
Frequently asked questions
Does it work without PASPA?
Yes, it can run with local configuration; PASPA adds centralised management and updates.
What happens if MQTT goes down?
SIP calls keep working; MQTT-dependent functions recover once the link is restored.
How is it updated?
Through packages uploaded and applied via the API, orchestrated from PASPA.
Which codecs are used?
The list is configurable per project; G.722 and Opus offer the best voice quality.
What is the difference between the operator panel and the cab?
The operator panel focuses on phonebook and operational calls; cab mode adds the PA selector.
Quick comparison
| Criterion | PASPA | Módulo SIP |
|---|---|---|
| Location | On-board server | Embedded hardware at each point |
| Function | Orchestration, rules and recording | Audio terminal and peripherals |
| Protocols | SIP, ARI, MQTT, REST | SIP, RTP, MQTT, REST, webhooks |
| End user | Engineering, maintenance and driver | Passenger, driver and operator |
Shall we talk about your on-board audio system?
Our sales and engineering team will help you define the solution for your fleet.