About this app

REDCOM® Sigma® Client is a SIP-based C2 softphone that provides secure voice, video, and chat with presence on Android™ phones and tablets.

Sigma Client is a stand-alone softphone app and not a VoIP service. To make calls, the app requires the REDCOM Sigma call controller. While it may work with other standards-compliant SIP and XMPP servers, we do not support third-party call and session controllers.

Product Highlights:
• Protects critical communications with 2048-bit RSA encryption
• Supports dual registration to two or more independent SIP servers
• Supports a range of standard and high-definition codecs including G.711, G.722, G.729, Opus, and Speex
• Fully AS-SIP compliant

Unified Communications Features:
• Real-time voice
• Full MLPP support
• Integrated PTT
• Point-to-point video
• XMPP chat

Other General Features:
• Call forwarding
• Call transfer (attended & blind)
• Call hold
• Call history (view & delete)
• Calling number delivery
• Three-way calling
• Missed call notifications
• Support for ICE
• Call encryption (TLS/SRTP)
• FIPS 140-2 validated encryption
• Mutual authentication
• Noise suppression
• Echo cancellation (device dependent)
• Provisioning
• Dial plan rules
• Auto start on bootup
• Emergency call handling by native dialer*

For more information on Sigma Client features, visit: https://www.redcom.com/products/sigma-client/

*Emergency Call Handling:
When a user dials an emergency number from Sigma Client on a device with telephony support, the app is designed to pass the dialed digits to the mobile device's native dialer, where the user can then attempt to complete the emergency call via their cellular carrier’s voice network. After handing off the dialed digits to the native dialer, the app is no longer involved in the call attempt. Once placed, the emergency call and any related location services are the responsibility of the cellular carrier. By default, the app treats ‘911’ as an emergency number and passes 911 calls to the native dialer.
The user can reconfigure the list of known emergency numbers within the app, which allows the user to control which dialed numbers, if any, are passed to the native dialer. Dialing emergency numbers from the app on a device without telephony support or reconfiguring the app to prevent emergency numbers from being passed to the native dialer will cause the app to process any emergency call as a VoIP call over the data network. Such calls can fail to complete due to any disruption of the app’s ability to communicate with its VoIP network service, such as power outages, lack of data network connectivity, etc. Placing a call through the VoIP network to report an emergency may also fail to direct the call to the correct emergency response center or determine the user's correct location. For these reasons, REDCOM recommends that emergency calls be placed over the cellular carrier’s network using the device’s native dialer, if available. For devices without telephony support, REDCOM recommends that users always have an alternative means of accessing emergency operator services in case of disruption of VoIP service. REDCOM will not be liable for errors, delays, costs, damages, injury, or death resulting directly or indirectly from using Sigma Client for emergency calls.

New features

New dark theme
Minor bug fixes

App Permissions

Allows an application to initiate a phone call without going through the Dialer user interface for the user to confirm the call.
Required to be able to access the camera device.
Allows applications to open network sockets.
Allows an application to record audio.
Allows an application to modify global audio settings.
Allows a calling application which manages it own calls through the self-managed ConnectionService APIs.
Allows access to the list of accounts in the Accounts Service.
Allows an application to read the user's contacts data.
Allows access to the vibrator.
Allows using PowerManager WakeLocks to keep processor from sleeping or screen from dimming.
Allows applications to access information about networks.
Allows an application to receive the ACTION_BOOT_COMPLETED that is broadcast after the system finishes booting.