Description Product Reviews Ring Generator Built-In Talkback Amplifier Transmit and ReceiveVolume Control Provides Two-Way Communication (Does Not Provide Door Unlock Capability) Compatible with all Valcom Doorplate Speakers Power Supply Included (VP-324) Valcom Power Units Every Valcom product is marked with either a positive, negative or neutral power unit. Simply add up the negative power units and then purchase a power supply with a greater value than the total power consumption of the system. If you have extra power units you can add speakers to the system at a later date, extra power is OK lower power will cause a performance problem on your paging system. One Valcom power unit = 50 mA, -24 Vdc 0 Reviews Hide Reviews Product Reviews