Voice (VoIP) Gateway PSTN Call Manager Module
The PSTN Call Manager provides the link between the terminal adapter’s dual POTS lines and remote VoIP devices. The PSTN Call Manager’s state machine manages the entire call sequence including, for example, the basic standard use case of a telephone unit going off hook, dialing a call, establishing a connection, sending and receiving voice content, and ending the call when the telephone is placed back on hook.
To provide a better user experience, voice prompts are used in situations where a universal standard feedback does not exist. For example, a voice prompt would not be used for a busy signal, but if a connection to the user’s VoIP proxy could not be established a voice prompt would inform the user of the situation and provide information on how to troubleshoot the situation.
When placing a call, the state machine processes the DTMF digit detection events from the POTS line and upon detecting the valid entry of a phone number it tries to establish a connection (an advanced configuration option allows the definition of what is valid; this allows the unit to be used in an office setting where, for example, a four-digit number starting with a ‘3’ is an inter-office call).
The PSTN Call Manager can establish connections to either a VoIP proxy server or directly to another VoIP handset. If a line is configured to use a proxy, a point-to-point call can still be made by using the “speed dial” option which is configured via the web-based configuration tool.
Once a connection is successfully established, voice data is streamed to and from the remote device. The PSTN Call Manager handles events during an active connection. The PSTN Call Manager handles incoming connection attempts, whether they occur when the line is inactive or in use. When the line is inactive, it will ring the telephone and the ring cadence can be configured to be different for each line or different per incoming phone number. When the line is in use, it interjects two short beeps into the voice stream to indicate there is an incoming call.
The PSTN Call Manager will also generate Caller ID information and send it out the POTS line at the appropriate time for standard display on a telephone. It does this for any incoming call, whether the phone is inactive or in use.
Supported PSTN Call Manager RFCs and Features
- Successful Connection
- Dial Tone
- User Busy
- Invalid Number
- Other Error Conditions
- Placing a Call On Hold
- Being Placed on hold
- Call Waiting
- Call Forwarding
- Conference calling
- Call Transfer
- Caller ID
- General Error Feedback.
- Off-hook erros
- Invalid Number
- RFC 3665 (Best Current Practices for SIP based PC based call flows)
- RFC 3666 (Best Current Practices for SIP based PSTN call flows)
Fusion VoIP Reference Design Modules
- Router Gateway
- VoIP Terminal Adapter
- Security Module
- Networking Module
- PSTN Call Manager
- Fusion RTOS
- Voice Processing Suite
- Hardware Drivers Module
- Support Module
*A reference design is a sample electronics circuit design that shows engineers how to utilize the latest developments in microchips in their own products. Using a reference design as a base, it is possible today for a device manufacturer to incorporate a new technology into existing designs in a few weeks, and have products available to ship not long after.
Available Reference Designs
