VLAN trunks formed using DTP may utilize either IEEE 802.1Q or Cisco ISL trunking protocols. Commonly found additional features are VLANs, trunking and QoS. Disabling Dynamic Trunking Protocol (DTP). Some radios made by ICOM are compatible with Motorola and SmarTrunk trunking systems. Digium Cloud Services include Switchvox Cloud service and SIP Trunking. Prior to supporting standardized IEEE 802.1Q tagging, 3Com used proprietary "Virtual LAN Trunking" (VLT). It included secure voice and data trunking services. MF is used for signaling in trunking applications. The trunking from that boiler room was removed, leaving just two straight funnels. Trunking and Distributed Split Multi-Link Trunking, ZTE's "Smartgroup", Huawei's "Eth-Trunk", or Connectify's Speedify. With sufficient channels, there is no need for trunking. EDACS was developed in competition with Motorola's Smartnet trunking system. They will provide simple trunking facilities for voice calls only. This system is not as common as the typical trunking method, but they do exist. The ballonets can be independently filled by using shut-off dampers in the air supply trunking.