Many First Responder agencies are looking to augment their current radio communications systems with a Push-to-Talk over Cellular system on a public cellular network, to help ensure that coverage is strong, to provide redundancy if their radio network fails, to equip more staff with cost-effective communications devices, and to provide the instant ability to communicate with other First Responder agencies in emergencies wherever they are. The SD7 mission critical PTT Handset and the optional VK7 Vehicle Kit provides this capability to First Responders to help them save lives. The SD7 Handset is an ideal replacement for legacy LMR two-way radios since it looks, feels and operates just like a handheld radio, but it operates on a cellular network.