Smart intercom stations for legacy intercom systems

Abstract

Smart buzzer systems for apartment buildings, where an intercom station in an apartment unit notifies the user of a request from a guest to unlock the building's door, sends the user's approval of the request to the door, and enables the user and the guest to talk to each other, are disclosed. The smart buzzer systems are enhanced with connectivity with mobile devices and mobile applications as well as automation. The intercom station includes an audio input-output circuit configured to process audio signals, which includes a line input buffer configured to process audio signals from a legacy base microphone through a wiring interface for a legacy intercom system to a processor and a line output driver configured to process audio signals from the processor to the legacy base speaker through the wiring interface fertile legacy intercom system.

What is claimed is: 
     
         1 . An intercom station apparatus for connection to a legacy intercom system, comprising:
 a station audio emission subsystem configured to emit a first audio signal;   a station audio reception subsystem configured to receive a second audio signal;   a talk feature configured to activate the station audio reception subsystem and a legacy base speaker;   a listen feature configured to activate a legacy base microphone and the station audio emission subsystem;   a wiring interface for the legacy intercom system;   a processor configured to interact with and control the station audio emission subsystem and the station audio reception subsystem; and   an audio input-output circuit configured to process audio signals, comprising:
 a line input buffer configured to process audio signals from the legacy base microphone through the wiring interface for the legacy intercom system to the processor, comprising:
 a first electrostatic discharge and transient protection subcircuit configured to receive a first input signal from the wiring interface for a legacy intercom system; 
 a first galvanic isolator and voltage scaler subcircuit; and 
 a first voltage buffer coupled to the first galvanic isolator and voltage scaler subcircuit, wherein the first voltage buffer is configured to transmit a first output signal to the processor; and 
 
 a line output driver configured to process audio signals from the processor to the legacy base speaker through the wiring interface for the legacy intercom system, comprising:
 a second voltage buffer configured to receive a second input signal from the processor; 
 a high-pass filter coupled to the second voltage buffer; 
 a second galvanic isolator and voltage scaler subcircuit coupled to the high-pass filter; and 
 a second electrostatic discharge and transient protection subcircuit coupled to the second galvanic isolator and voltage scaler subcircuit and configured to transmit a second output signal to the wiring interface for the legacy intercom system. 
 
   
     
     
         2 . The intercom station apparatus of  claim 1 , wherein the station audio emission subsystem is a station speaker, wherein the first audio signal is sound, wherein the station audio reception subsystem is a station microphone, and wherein the second audio signal is sound. 
     
     
         3 . The intercom station apparatus of  claim 1 , wherein the first voltage buffer is a first operational amplifier, and wherein the second voltage buffer is a second operational amplifier. 
     
     
         4 . The intercom station apparatus of  claim 1 , wherein the first electrostatic discharge and transient protection subcircuit comprises a first electrostatic discharge resistor and a first transient-voltage-suppression diode, and wherein the second electrostatic discharge and transient protection subcircuit comprises a second electrostatic discharge resistor and a second transient-voltage-suppression diode. 
     
     
         5 . The intercom station apparatus of  claim 1 , wherein the first galvanic isolator and voltage scaler subcircuit comprises a first transformer, and wherein the second galvanic isolator and voltage scaler subcircuit comprises a second transformer. 
     
     
         6 . The intercom station apparatus of  claim 5 , wherein the first transformer is 1:1. 
     
     
         7 . The intercom station apparatus of  claim 5 , wherein the second transformer is 1:1. 
     
     
         8 . The intercom station apparatus of  claim 5 , wherein the first galvanic isolator and voltage scaler subcircuit further comprises a first voltage scaler coupled to the first transformer, and wherein the second galvanic isolator and voltage scaler subcircuit further comprises a second voltage scaler coupled to the second transformer. 
     
     
         9 . The intercom station apparatus of  claim 8 , wherein the first voltage scaler comprises:
 a first voltage divider coupled to the first transformer, and   a second voltage divider coupled to the first voltage divider; and   wherein the second voltage scaler comprises a third voltage divider.   
     
     
         10 . The intercom station apparatus of  claim 9 , wherein the first voltage divider comprises a plurality of resistors, and wherein the first voltage divider generates a ratio of approximately 50%. 
     
     
         11 . The intercom station apparatus of  claim 9 , wherein the second voltage divider comprises a plurality of resistors. 
     
     
         12 . The intercom station apparatus of  claim 9 , wherein the second voltage divider biases a signal to around half of a supply voltage. 
     
     
         13 . The intercom station apparatus of  claim 9 , wherein the third voltage divider comprises a plurality of resistors, and wherein the third voltage divider generates a ratio of approximately 4.5%. 
     
     
         14 . The intercom station apparatus of  claim 5 , wherein the high-pass filter comprises a capacitor with a capacitance based on an impedance of the second transformer. 
     
     
         15 . The intercom station apparatus of  claim 5 , wherein the second transformer comprises a plurality of windings, and wherein a DC resistance of each winding of the plurality of windings of the second transformer is greater than a resistance of a legacy station speaker. 
     
     
         16 . The intercom station apparatus of  claim 5 , wherein the second transformer supports a signal range of 200 Hz to 4,000 Hz. 
     
     
         17 . The intercom station apparatus of  claim 1 , wherein the line input buffer further comprises a voltage-limiting subcircuit coupled to the first voltage buffer, wherein the voltage-limiting subcircuit limits an input to the first voltage buffer to within a predefined threshold. 
     
     
         18 . The intercom station apparatus of  claim 17 , wherein the voltage-limiting subcircuit comprises a Schottky barrier diode. 
     
     
         19 . The intercom station apparatus of  claim 1 , wherein the intercom station apparatus is configured to interact with a base and a backend cloud-computing service (CCS). 
     
     
         20 . An intercom station apparatus for connection to a legacy intercom system, comprising:
 a station audio emission subsystem configured to emit a first audio signal;   a station audio reception subsystem configured to receive a second audio signal;   a talk feature configured to activate the station audio reception subsystem and a legacy base speaker;   a listen feature configured to activate a legacy base microphone and the audio emission subsystem;   a wiring interface for the legacy intercom system;   a processor configured to interact with and control the station audio emission subsystem and the station audio reception subsystem; and   an audio input-output circuit configured to process audio signals, comprising:
 a line input buffer configured to process audio signals from the legacy base microphone through the wiring interface for the legacy intercom system to the processor, comprising:
 a first galvanic isolator and voltage scaler subcircuit configured to receive a first input signal from the wiring interface for a legacy intercom system; and 
 a first voltage buffer coupled to the first galvanic isolator and voltage scaler subcircuit, wherein the first voltage buffer is configured to transmit a first output signal to the processor; and 
 
 a line output driver configured to process audio signals from the processor to the legacy base speaker through the wiring interface for the legacy intercom system, comprising:
 a second voltage buffer configured to receive a second input signal from the processor; 
 a high-pass filter coupled to the second voltage buffer; and 
 a second galvanic isolator and voltage scaler subcircuit coupled to the high-pass filter and configured to transmit a second output signal to the wiring interface for the legacy intercom system.