Spec Sheet Preview: The Alpha Communications® / S.T.R.™ SP300-12K intelligent controller is used only with the HT3011W ReliaBUS™ series intercom and VH30-2D videointercom systems. The SP300-12K provides the intelligent 'BUS' circuitry needed to control the ReliaBUS™ system functions. Each SP300-12K gets its power from the NTR211 power supply. All SP300-12K field connections are positive screw terminal type, or plug-in type. For systems up to 56 apartments, use 2- SP300-12K units. For systems of 57-88 apartments, us …