About Us - Telisys Phone Systems Santa Rosa Providing telecom and computer network solutions since 1985. A TELECOM CONCEPTS COMPANY Home Products Client/Project Examples SIP... as an opportunity and are now offering their clients computer based, VoIP phone systems. Unfortunately many VoIP systems are expensive, unproven and lack many important features commonly... found on traditional phone systems. Also, many of these systems are extremely vulnerable to network attacks and unwanted conversation monitoring and can unnecessarily slow down your...