The Potomac 1901-4 digital antenna monitor is a 5 1/4 inch unit containing control/measurement circuitry for up to 4 towers, digital display of all measurements, local operating controls, and an interface to a remote control system. The control/measurement circuitry for each tower is contained in a separate module. The modules plug into the rear of the unit, and may be easily added to an expanding station.The 1901-4 provides a direct interface to a remote control device. Each of the control/measurement modules (one for each tower in the system) provides continuous analog outputs relative to the ratio and phase for each tower. These outputs may be connected to the telemetering inputs of the remote control device. The outputs may also be connected to an array of meters to prove a continuous and simultaneous display of each tower in the system. FCC authorization number: IJ3PI1900 Digital display of ratio and phase of up to 4 towers Same phase accuracy as the industry standard AM-19 Modular design simplifies expansion, reduces downtime Provides continuous analog outputs of all tower measurements Fully compatible with any standard remote control system Simplified operating controls, local or external Measurements for up to 4 towers in 5 1/4 inch rack height