- Cisco Systems Inc.
- Polycom Inc. (Plantronics)
- Mitel Network Communications
- Verizon Communications Inc.
- AT&T Inc.
- Avaya Inc.
- NEC Corporation
- Ringcentral Inc.
- 8x8 Inc.
- Shoretel Inc.
- Vidyo Inc. (Enghouse Systems Limited)
- Arkadin Cloud Communications (NTT)
- West Corporation
- BT Group