February 7, 2022 by Kenneth McKinney

Critical Connect ISSI Is First to Achieve P25 CAP Compliance

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Industries: 9-1-1 & Law Enforcement Federal Fire & EMS

Topics: ASTRO P25 Infrastructure

Motorola Solutions’ Critical Connect became the first product to successfully complete the Department of Homeland Security (DHS) Project 25 Compliance Assessment Program (P25 CAP) testing for its Inter RF Sub System Interface (ISSI). As a P25 CAP compliant solution, Critical Connect is now on the DHS list of grant-eligible products, making it possible for customers to apply for and, if the application is approved, use federal grant funds in its procurement. 

What is Critical Connect?

Critical Connect from Motorola Solutions provides cloud-based interoperability between P25 land mobile radio (LMR) systems to eliminate barriers and unify communications for all responders. While Critical Connect also provides interoperable communications between users on P25 LMR networks and those on broadband PTT, as well as non-P25 LMR networks, the P25 CAP testing applied only to P25 LMR to P25 LMR communication.

What is P25 CAP? 

The P25 CAP is a formal, independent process for ensuring communications equipment is compliant with the P25 standard by testing it against the standard and publicly publishing the results. Voluntary vendor participation in this open-standards testing process demonstrates interoperability among different suppliers’ products. 

P25 CAP testing takes place at a DHS-recognized and ISO 17025 accredited labs that rigorously test the equipment to the test cases within the P25 CAP Compliance Assessment Bulletins. Only communications equipment that has satisfied those testing requirements, with the test results reviewed and approved by the DHS Science & Technology Directorate, can be considered “P25 CAP Compliant.” 

What was tested?

The Critical Connect ISSI testing was conducted for both Frequency Division Multiple Access (FDMA) and Time Division Multiple Access (TDMA) P25 networks. The test cases covered the use of the Critical Connect ISSI to connect two Radio Frequency SubSystems (RFSS) supporting the tests. 

Individual ISSI to RFSS tests included:

  • Unit Registration
  • Talkgroup Registration
  • Group Voice Calling
  • Broadcast Calling
  • Announcement Group Calling
  • Emergency Group Calling
  • Encrypted Group Calling

The test cases also covered the use of the Critical Connect ISSI to connect an RFSS with an integrated console subsystem with another RFSS supporting the test (P25 CAP refers to this as a Console Sub System Interface (CSSI) to RFSS test). Testing with a console-only subsystem was not included in the assessment.

Individual CSSI to RFSS tests included:

  • Talkgroup Registration
  • Group Voice Calling
  • Broadcast Calling
  • Announcement Group Calling
  • Emergency Group Calling
  • Encrypted Group Calling

The tests were executed in the inter-WACN and inter-System ID configurations. All role combinations required for each test case passed, except for those test cases/role combinations identified as Unsupported. There were no failed test cases.

Why does compliance matter to you?

First, compliant solutions appear on the P25 CAP Approved (Grant-Eligible) Equipment page, which is referenced by various federal grant programs as part of their application review and approval process. The page provides these grant programs with easy access to the Summary Test Report (STR) and Supplier’s Declaration of Compliance (SDOC) documents submitted by vendors upon completion of the P25 CAP testing.

Second, as stated in the DHS Science & Technology Directorate document, P25 CAP Compliance: What Should It Mean to You?, “P25 CAP provides responders with confidence that the communications equipment they use has been tested against the appropriate P25 standards and determined interoperable, regardless of manufacturer.” 


Critical Connect improves collaboration between agencies, making it easier for them to share information regardless of device or network. As demonstrated by the P25 CAP testing, one physical link from your ASTRO 25 network to Critical Connect provides interoperable communication with other P25 networks. 

Though not included in the testing, that same physical link to Critical Connect can also provide interoperable communication between users on your ASTRO 25 network and those on AT&T’s EPTT, Verizon’s PTT+, Verizon’s Group First Response, and WAVE PTX broadband PTT services, as well as MOTOTRBO networks and other LMR systems.

Motorola Solutions has long distinguished itself as a leader in the development of industry standards for mission critical communications. That our Critical Connect solution for interoperability is the first product to achieve P25 CAP compliance for ISSI is further testament to our commitment to standards-based communications for public safety.

Contact us to find out more about our solutions and services.

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