Patent Publication Number: US-2011069608-A1

Title: System for providing backup programming at radio or television transmitter

Description:
FIELD OF THE INVENTION 
     The present application relates generally to a media transmission system and, more particularly, to a transmitter system providing back-up media programming for a radio and/or television transmission system. 
     BACKGROUND OF THE INVENTION 
     Transmission systems such as radio or television broadcast stations are widely used to transmit media programming, such as radio and/or television programs, to a large number of listeners and/or viewers. Traditional transmission systems such as broadcast stations include a studio connected to a transmission station via a transmission medium. The studio controls the programming media to be transmitted. More specifically, media programming is selected and is processed to generate a media signal that is delivered over the transmission medium to the transmission station. The transmission station receives the media signal and ultimately transmits the program media to the listeners/and or viewers such as by wireless broadcasting in the frequency bands designated for AM, FM, television (e.g., UHF and VHF) or satellite transmissions. 
     Many radio and television broadcast stations do not have their actual transmission station (e.g., a transmitter and broadcast tower) located on the same property as their programming studio. In fact, many broadcast stations share a single transmission station. For example, many radio and television broadcast stations comprise a studio that is located 10, 15 and sometimes as many as 30 miles away from the actual transmitter and tower. Some radio and television stations employ a microwave relay tower. A program signal to be broadcast via the remote tower is sent by microwave from the site of the studio to a similar microwave receptor on the grounds where the transmitter and tower are located. The transmitted microwave signal is then converted into a signal that can be broadcast to the general public, for example. Thus, the transmission medium is a microwave or other wireless link or a wired link (e.g., a T1, ISDN and/or other links) configured to effectively span geographic distances between the studio and the transmission station. 
     Since the transmission station is located remotely from the studio, however, a transmission failure between the studio and the transmission station can cause disruptions in the media programming received by the listeners and/or viewers. Further, a transmission failure between the studio and the transmission station may not be detected immediately. As a result, listeners and/or viewers may experience media disruption for an indefinite amount of time. 
     A need therefore exists for more reliable transmission of signals between a studio and transmitter of a broadcast station. 
     SUMMARY OF THE INVENTION 
     As noted above, exemplary embodiments of the present invention address at least the above problems and/or disadvantages, and provide at least the advantages described below. 
     In accordance with an exemplary embodiment of the present invention, a media transmission system is provided for selectively transmitting backup programming media in which a transmitter station is connected to a remote media station via a transmission medium. The media transmission system generates a source media signal including media programming via a media programming source located at the media station; generates an Ethernet media signal including backup media programming via an Ethernet programming source located a the media station; receives the source media signal at the transmitter station and transmits the media programming based on the source media signal; receives the Ethernet media signal at the transmitter station and stores the backup media programming in a storage device based on the Ethernet media signal; detects a fault on the transmission medium, or is otherwise instructed to switch to transmission of stored backup media programming; retrieves the stored backup media programming and generates a backup media signal including the backup media programming; and transmits backup media programming based on the backup media signal. 
     Another exemplary embodiment of the present invention provides for storing the backup media programming while simultaneously transmitting the source media signal. 
     Another exemplary embodiment of the present invention provides for multiplexing the source media signal and the Ethernet media signal for outputting a data signal to the transmitter station. 
     Still another exemplary embodiment of the present invention provides for demultiplexing the data signal received by the transmitter station for obtaining the source media signal and the Ethernet media signal. 
     Still another exemplary embodiment of the present invention provides for compressing the source media signal prior to multiplexing the source media signal with the Ethernet media signal. 
     Another exemplary embodiment of the present invention provides for decompressing the source media signal after de-multiplexing the data signal. 
     Yet another exemplary embodiment of the present invention provides for detecting a fault on the transmission medium based on Cyclic Redundancy Check (CRC) bits included with the data signal. 
     Still another exemplary embodiment of the present invention provides for the backup media programming being different than the media programming. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other exemplary features, aspects and advantages of the present invention will become more apparent from the following detailed description of certain exemplary embodiments thereof when taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a schematic block diagram of a media transmission system according to an exemplary embodiment of the present invention; 
         FIG. 2  is a flow diagram of an illustrative method for transmitting backup media programming in a media transmission system according to an exemplary embodiment of the present invention; 
         FIG. 3  is a schematic block diagram of a media transmission system according to an alternative exemplary embodiment of the present invention; 
         FIG. 4  is a schematic block diagram a video transmission system including a media station, a transmitter station and a transmission medium for transmitting video media programming according to an exemplary embodiment of the present invention; 
         FIG. 5  is a schematic block diagram of a digital FM media station according to an exemplary embodiment of the present invention; 
         FIG. 6 . is a schematic block diagram of a digital FM transmitter station according to an exemplary embodiment of the present invention; 
         FIG. 7 . is a schematic block diagram of an AM media station according to an exemplary embodiment of the present invention; 
         FIG. 8  is a schematic block diagram of an AM transmitter station according to an exemplary embodiment of the present invention; 
         FIG. 9  is a schematic block diagram of a media transmission system according to an alternative exemplary embodiment of the present invention; and 
         FIG. 10  is a schematic block diagram of a media transmission system including dual media stations and a single transmitter station according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     A media transmission system transports high quality audio and/or video media programming from a media station to a transmitter station via a transmission medium. In the event of a transmission medium or equipment failure, there is no media transmission. A common problem, which is addressed by exemplary embodiments of the present invention, is how to quickly recover media transmission in the event the transmission medium or other equipment fails. 
     As described below, a media transmission system constructed in accordance with exemplary embodiments of the present invention comprises a non-volatile storage device. Once the media transmission system detects a loss of communication with the media station, backup media programming stored in the storage device can be played to avoid dead air time. The backup media programming may be stored as computer files. Accordingly, a number of files may be linked together and played in series and then looped to the beginning of the series. Once communication to the media station is resolved, the media transmission system can again transmit the media programming. Further, users can operate the media transmission system to selectively switch alternative programming on and off as desired without the necessity of a faulty transmission medium or equipment failure (e.g., to transmit emergency broadcast messages). 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views,  FIG. 1  generally shows a media transmission system  10  including a media station  12 , a transmitter station  14 , and a transmission medium  16 . The media station  12  selects and processes media programming. The transmitter station  14  is located remotely from the media station  12  and ultimately transmits the media programming provided by the media station  12  in real-time. 
     The transmission medium  16  connects the media station  12  with the transmitter station  14  for communicating signals and/or data therebetween. The transmission medium  16  is a telecom network that can comprise, but is not limited to, E1 and/or T1, or T3 transmission media, Ethernet, a radio link, free air optics, SONET, among other transmission links and modalities. The data communicated between the media station  12  and the transmitter station  14  includes, but is not limited to, digital and/or analog audio signals, digital and/or analog video signals, Ethernet data packets, Cyclic Redundancy Check (CRC) bits, address resolution protocol (ARP) data, and Operation, Administration and Maintenance (OAM) data. Further, the data delivered over the transmission medium  16  may comprise compressed and/or decompressed digital data. 
     The media station  12  comprises at least one media programming source  18  for generating a source media signal including media programming, an Ethernet media source  20  including one or more inputs or ports for receiving signals from a media programming source, a station controller  22 , and a station network module  24 . The media programming source  18  may comprise a traditional analog media programming source, a traditional digital media source, or a High Definition (HD) digital media source that generates an HD digital media signal. Further, the programming media provided by the traditional media sources may be different than the programming media provided by the HD digital media source. 
     Various audio processing modules such as a compression module  26  may also be included with the media station  12 . The compression module  26  compresses the source media signal and outputs a compressed source media signal. Additionally, the compression module  26  may comprise one or more sample rate converters for adjusting the sampling and/or data rate of a HD digital programming media to allow synchronization with the transmission medium  16 . Changing the data rate allows the digital audio interface to run at a different speed and/or with a different source from the transmission rate of data communicated over the transmission medium  16 . For example, the available rates for audio carried over a transmission medium  16  such as a T1/E1 interface include, but are not limited, to 48 K and 32 K samples per second. In addition, the station network module  24  and the transmission network module  30  can handle incoming audio at rates including, but not limited to, 48 K, 44.1 K and 32 K samples per second. For incoming audio samples received at 44.1 K, the audio may be converted to 48 K samples per second by default. 
     The Ethernet media source  20  includes an Ethernet media source input. The Ethernet media source  20  provides backup media programming, and generates an Ethernet media signal that comprises backup media programming. The backup media programming may be different than media programming generated by the media programming source  18 . The transmission of the backup media programming is described in greater detail below. Additionally, an Ethernet switch  21  may be included with each of the media station  12  and transmitter station  14  for routing data to various corresponding modules. 
     The station controller  22  is in electrical communication with the Ethernet media input for outputting at least one user selection signal for selecting transmission of either the media programming source  18  or a backup media source included with the transmitter station  14 , as described in greater detail below. In addition, the station controller  22  may output public alert messages and/or other various alerts. 
     The station network module  24  is in electrical communication with the media programming source  18  and the Ethernet media source  20  for further processing the source media signal, the Ethernet media signal, and/or the HD digital media signal. Specifically, the station network module  24  multiplexes the source media signal, the Ethernet media signal, and/or the HD digital media signal to generate a single data signal  28 . The data signal  28  is then delivered to the transmission medium  16 . The station network module  24  may further encapsulate the source media signal, the Ethernet media signal, and/or the HD digital media signal prior to generating the data signal. 
     The transmitter station  14  comprises a transmitter network module  30 , storage device  32 , a selection module  34 , a controller  36 , and a transmitter  38 . The transmitter network module  30  is included with the remotely located transmitter station  14  for receiving the data signal  28 . The transmitter network module  30  demultiplexes the data signal to obtain the source media signal, the Ethernet signal, and/or the HD digital media signal. Further, the transmitter network module  30  may de-encapsulate the source media signal, the Ethernet signal and/or the HD digital media signal if the media signal, the Ethernet signal, and/or the HD digital media signal are encapsulated. Similar to the media station  12 , the transmitter station  14  may comprise various processing modules, such as a decompression module  40  for decompressing a compressed the source media signal to obtain the source media signal. 
     The storage device  32  is in electrical communication with the transmitter network module  30  for storing backup media programming. As discussed above, the media station  12  comprises an Ethernet media source  20  that generates an Ethernet media signal including backup media programming. The transmitter network module  30  obtains the Ethernet media signal after demultiplexing the data signal  28 . After demultiplexing the data signal  28 , the transmitter network module  30  delivers the Ethernet media signal to the storage device  32  for storing the backup media programming. As mentioned above, the backup media programming may be different than the media programming to be transmitted by the transmitter station  14  during real-time. 
     The selection module  34  is selectively operable in a source mode for delivering the source media signal to the transmitter  38  for transmitting the media programming to listeners and/or viewers in real-time. Further, the selection module  34  is selectively operable in a backup mode for delivering a backup signal to the transmitter  38  for transmitting the backup media programming to listeners and/or viewers, as discussed in greater detail below. As previously mentioned, the media station  12  may include a station controller  22  in electrical communication with the Ethernet media input for outputting at least one user selection signal. Accordingly, the selection module  34  can be controlled by a user of the station controller  22  located at the media station  12  for selecting one of the source mode or the backup mode of the selection module  34 . The selection module  34  may include a lighting protection system and drop-out relays to quickly switch over to the backup mode if the transmission of backup media programming is required. It can be appreciated that an additional selection module, i.e., a backup selection module  30 ′ may be included which operates in case the selection module fails. The backup selection module  30 ′ operates in same manner as the selection module for delivering either the source media signal or the backup signal to the transmitter  38 . 
     The controller  36  is in electrical communication with the transmitter network module  30 , the storage device  32 , and the selection module  34 . The controller  36  receives at least one of the source media signal, Ethernet media signal, and/or HD digital media signal from the transmitter network module. The source media signal may be delivered to the controller  36  prior to de-encapsulation, after de-encapsulation, and/or after de-compression. In addition, the controller  36  may determine whether the data transmission between the media station  12  and the transmitter station  14  is faulty. A faulty data transmission comprises, but is not limited to, the station network module  24  becoming disabled, a corrupt data signal, an incorrectly de-encapsulated source media signal, and/or incorrectly decompressed source media signal. As mentioned earlier, the data delivered over the transmission medium  16  may comprise CRC bits. Accordingly, the error in the data signal may be determined using a Cyclic Redundancy Check to analyze the CRC bits. 
     When the controller  36  determines that the transmission medium  16  is functional i.e., is not faulty, the media programming is preferably transmitted in real-time while the storage device  32  is simultaneously stored with the backup media programming provided by the remotely located Ethernet media source  20 . Accordingly, the storage device  32  can be constantly loaded with backup media programming. If the transmission medium  16  is determined to be faulty, or a user selects transmission of the backup media programming via the station controller  22 , the controller  36  selects the backup mode of the selection module  34  for transmitting backup programming media to listeners and/or viewers. More specifically, after selecting the backup mode, the controller  36  retrieves the backup media programming from the storage device  32  and generates a backup media signal including the backup media programming. In response to operating in the backup mode, the selection module  34  receives the backup media signal from the controller  36  and delivers the backup media signal to the transmitter  38 . Upon receiving the backup media signal, the transmitter  38  transmits the backup media programming to listeners and/or viewers in place of the media programming. 
     Accordingly, disruption of media transmission to the listeners and/or viewers may be prevented even when a complete disconnection between the media station  12  and the transmitter station  14  occurs. Furthermore, a more accurate determination of a faulty transmission medium is achieved since faulty detection may be based on actual errors in the data signal, as opposed to analyzing the audio signal to determine silence and/or lapses in audio transmission. 
     Referring now to  FIG. 2 , the media transmission system  10  implements a method generally shown at  200  to transmit backup media programming in accordance with an exemplary embodiment of the present invention. The method starts at step  202  and proceeds to step  204  during which the media programming source  18  located at a media station  12  generates a source media signal including media programming to be transmitted in real-time, i.e. live. In step  206 , the Ethernet programming source  20  located at the media station  12  generates an Ethernet media signal including backup media programming for backup transmission. The transmitter station  14  receives both the source media signal and the Ethernet media signal in step  208 . In step  210 , a transmitter  38  included with the transmitter station  14  transmits the media programming in real-time based on the source media signal. In step  212 , the Ethernet media signal is delivered to a storage device  32  and the backup media programming is stored therein, preferably while simultaneously transmitting the media programming in real-time. 
     The controller  36  determines whether the data connection between the media station  12  and the transmitter station  14  is faulty, or a user has selected alternate programming, in step  214 . If the data connection is not faulty, the method returns to step  210  and continues to transmit the media programming. If a faulty data connection, or a user&#39;s selection of alternate programming, is detected in step  214 , then the controller  36  generates a backup signal in step  216 . For example, if the transmission medium  16  or link (e.g., a T1 line) is broken or disrupted, or if the media station  12  becomes inoperable, an error at the transmission medium  16  or an error in the de-encapsulation or an error in the decompression would be detected and reported to the controller  36 . The backup signal comprises the backup media programming stored in the storage device  32 . In step  218 , the transmitter  38  receives the backup media signal and transmits the backup media programming. In step  220 , the controller  36  determines whether the data connection between the media station  12  and transmitter station  14  has been restored and is functioning properly or a user requests cessation of the backup programming media transmission. If the data connection is functioning properly, the controller  36  stops generating the backup signal in step  222  and the method returns to step  210  to transmit the media programming. If the data connection is not yet functioning properly, the method returns to step  218  and the transmitter  38  continues to transmit the backup programming media. 
     Referring now to  FIG. 3 , an alternative exemplary embodiment of the media transmission system  10  is generally shown. The media transmission system  10  operates similar to media transmission system  10  of  FIG. 1 , which is described in detail above. The media transmission system  10  includes a redundant transmission medium  16  comprising a primary transmission line  28  and a secondary transmission line  29 . The primary transmission line  28  communicates the data signal including the source media programming, similar to the transmission medium  16  described above. The secondary transmission line  29  communicates a redundant data signal between the station network module  24  and the transmitter network module  30 . The redundant data signal is identical to the data signal communicated over the primary transmission line  28  and is used to communicate data from the source media signal to transmitter network module  30  in case the primary transmission line  28  fails. Specifically, the transmitter network module  30  selectably receives the data signal on the primary transmission line  28  and redundant data signal on the secondary transmission line  29 . Further, the transmitter network module  30  analyzes the CRC packets included with the data signal on line  28  and the redundant data signal on line  29 . Based on the CRC analysis, the transmitter network module  30  determines whether the primary data signal on line  28  is of higher quality than the redundant data signal on line  29 . When the primary transmission line  28  fails, or when the transmission quality of the redundant data signal on line  29  exceeds that of the data signal on line  28 , the transmitter network module  30  may select the secondary transmission line  29  to receive the redundant data signal. Accordingly, communication of the source media signal between the station network module  24  and the transmitter network module  30  can be sustained even though the primary transmission line  28  fails. 
     The media transmission system  10  further includes switch-to-protect modules  42 ,  42 ′ and an auxiliary transmission medium  44 . A first switch-to-protect module  42  is included in the media station  12  and is connected between the media programming source  18  and the compression module  26 . A second switch-to-protect module  42 ′ is included in the transmitter station  14  and is connected between the decompression module  28  and the transmitter  38 . The auxiliary transmission medium  44  is connected between switch-to-protect modules  42 ,  42 ′. The auxiliary transmission network  44  may include an auxiliary network module similar to the station and transmitter network modules  24 ,  30 , a microwave data link, a spare copper line pair, or any other transport system that connects the media station  12  and the transmitter station  14  during failure. In this way, the analog audio data completely bypasses the transmission medium  16  to restore a complete media path. If the auxiliary transmission medium  44  is not configured or desired, and the network or the station network module  24  and/or the transmitter network module  30  fail, the final level of protection is that backup media programming is transmitted by the transmitter  38 , as described in greater detail below. 
     The switch-to-protect modules  42 ,  42 ′ operate to select the auxiliary transmission medium  44  to provide an auxiliary data path for delivering the source media signal to the transmitter  38  if both the primary and secondary transmission lines  28 ,  29  fail. Although  FIG. 4  shows a first switch-to-protect module  42  included with the media station  12  and a second switch-to-protect module  42 ′ included with the transmitter station  14 , it can be appreciated that only one switch-to-protect module  42  may be used with either the media station  12  or the transmitter station  14 . 
     More specifically, the switch-to-protect modules  42 ,  42 ′ include drop-out relays (not shown) operable in a normal position and an auxiliary position. While operating in the normal position, the drop-out relays included with the first switch-to-protect module  42  provide a circuit path between the media programming source  18  and the compression module  26 , and the drop-out relays included in the second switch-to-protect module  42 ′ provide a circuit path between the decompression module  40  and the transmitter  38 . Accordingly, the primary data signal is communicated from the media station  12  to the transmitter station  14  via the redundant transmission medium  16 . However, if the station network module  24  and/or the transmitter network module  30  detects that both the primary and secondary transmission lines  28 ,  29  have failed, a drop-out relay control signal is output to each of the first and second switch-to-protect modules  42 ,  42 ′ to induce the auxiliary position of the drop-out relays. In addition, if station network module  24  and/or the transmission network module  30  never powers on or a processor or other failure of the station network module  24  and/or transmitter network module  30  occurs, the first and second switch-to-protect modules  42 ,  42 ′ may be selected to operate in the auxiliary position by default. 
     While operating in the auxiliary position, the drop-out relays included with the first and second switch-to-protect modules  42 ,  42 ′ select the auxiliary transmission medium  44 . Accordingly, the source media signal is communicated from the media station  12  to the transmitter station  14  via the auxiliary transmission medium  44  even though both the primary transmission line  28  and the secondary transmission line  29  of the redundant transmission medium  16  are faulty. 
     Accordingly, at least one exemplary embodiment of the present invention provides several levels of transmission fault protection. For example, at least one exemplary embodiment of the invention provides a primary transmission line  28  and a secondary transmission line  29  with very robust circuit protection, so that hardware failures are limited. If the primary line  28  fails, a secondary transmission line  29  is selected to communicate the redundant data signal for transmitting the source media. 
     If both the primary transmission line  28  and the secondary transmission line  29 , or the station network module  24  and/or the transmitter network module  30  fail, the auxiliary position of the drop-out relays are induced to select the auxiliary transmission medium  44 , which provides an alternative transmission link for communicating the media station  12  with the transmitter station  14 . Finally, if the auxiliary transmission medium  44  fails or is unavailable, the backup media programming is retrieved from the storage device  32  and is transmitted. 
     Lightning protection (not shown) may also be included with the transmission lines  28 ,  29 . For example, one or more fuses may be wired in series with each transmission line  28 , 29 , and a protector device may be wired from each transmission line  28 , 29  to ground so that if a significant lightning transient is coupled to the transmission medium  16 , the protector device clamps the transient to ground. If the transient goes beyond the current carrying ability of the clamping device, the fuse opens up, protecting the media transmission system  10  from further damage. In addition, a circuit board may be designed so that the traces can handle the extra current present during a normal lightning strike. 
     As discussed above, a primary transmission line  28  and a secondary transmission line  29  may be included to provide redundancy i.e., redundant transmission of the media programming. One of the two transmission lines  28 ,  29  may be used to transmit the data from the media station  12  to the transmitter station  14 . Both the primary transmission line  28  and the secondary transmission line  29  are active and configured in a typical installation. As discussed above, both lines  28 ,  29  preferably carry the same media programming. The transmitter network module  30  receives and decodes information from the primary transmission line  28  when the primary transmission line  28  is functional and selected. 
     The transmitter network module  30  simultaneously monitors the transmission quality of both transmission lines  28 ,  29  by analyzing a CRC value that is periodically encoded into the data stream communicated by each transmission line  28 ,  29 . The CRC value preferably matches a calculation determined from the other bits in the transmission lines  28 ,  29 . Short errors in the CRC calculation are ignored. However, if the error condition persists, the transmitter network module  30  determines a line failure on the selected transmission line  28 ,  29 . As long as the primary transmission line  28  has acceptable quality, the transmitter network module  30  continues routing data through the primary transmission line  28 . However, if the CRC calculation of the primary transmission line  28  is not correct for a sufficient duration, the transmitter network module  30  selects the secondary transmission line  29  and continues operating normally, assuming the CRC analysis of the secondary transmission line  29  is correct. 
     After selecting the secondary transmission line  29 , the transmitter network module  30  continues to monitor both transmission lines  28 ,  29 . If the quality of the primary transmission line  28  recovers, the transmitter network module  30  may reactivate the primary transmission line  28  to communicate the media source programming. If the quality of the secondary transmission line  29  is determined to be insufficient as well as the primary transmission line  28 , the transmitter network module  30  resorts to the next level of protection. That is, if both transmission lines  28 ,  29  fail, or if there is an internal failure on the station network module  24  and/or the transmitter network module  30 , the transmitter network module  30  has the ability to switch the analog inputs or outputs to the auxiliary transmission medium  44 . The drop-out relays on the unit are energized such that the auxiliary position is induced and the auxiliary transmission medium  44  is selected. If the station network module  24  and/or the transmitter network module  30  fail, or if the transmitter network module  30  detects an external failure condition, the drop-out relays are operated in the auxiliary position and the auxiliary transmission medium  44  is automatically connected. For example, the drop-out relays can operate in the auxiliary position when de-energized such that the auxiliary transmission medium  44  is selected. When the drop-out relays are energized, the normal position is induced and the media transmission system  10  operates as described above. 
     Referring now to  FIG. 4 , a video transmission system  10 ′ including a media station  12 , a transmitter station  14  and a transmission medium  16  for transmitting video media programming is generally shown in accordance with an exemplary embodiment of the present invention. The video transmission system  10 ′ operates similarly to the media transmission system  10  of  FIG. 1  described in detail above. The video media will almost always include audio; however, the audio is not explicitly shown to simplify the drawing. The video transmission system  10 ′ utilizes a high bandwidth transmission medium for handling the increases bandwidth required for transporting the video media  19 . The high bandwidth transmission medium includes, but is not limited to T3 line, SONET, or Ethernet. The backup media programming provided from the media station  12  via the Ethernet media source  20  is backup video media programming. Accordingly, the file storage device  32  included in system of  FIG. 3  is generally greater than the file storage device included in  FIG. 1  since the backup video media data is of greater file size. 
       FIGS. 5-10  illustrate alternative exemplary embodiments of the present invention. For example,  FIG. 5  depicts an exemplary embodiment of a digital FM media station. The digital FM media station includes a media station  12  and a transmitter station  14  that are separated from one another by several miles. The media programming is generated and stored at the media station  12 , while the transmitter station  14  includes a transmitter  38  for transmitting the media programming in real-time. Multiple signal streams can be sent from the media station  12  to the transmitter station  14 . 
       FIG. 6  depicts an exemplary embodiment of a digital FM transmitter station. The station network module  24  and/or the transmitter network module  30  allow the transport of stereo full bandwidth audio signal, with an optional data channel, over multiple timeslots of a transmission medium  16  such as a T1/E1 link. The modules  24  and  30  are program channel access units (PCAUs) that can be combined into a single device referred to as a PCAU suite  50 . The PCAU suite  50  can be provided at both ends of the audio link and configured to operate as the corresponding one of the modules  24  and  30 . The station network module  24  and/or the transmitter network module  30  have selectable digital/analog audio interfaces. Additionally, the station network module  24  and/or the transmitter network module  30  add an optional RBDS data channel, provide lower end-to-end delay, and add an external audio timing synchronization port. The station network module  24  and/or the transmitter network module  30  preferably pass an audio signal in both directions simultaneously. 
     The station network module  24  is used at the media station  12  and the transmitter network module  30  is used at the transmitter station  14 . A mono or stereo audio source is connected to a transmit audio port (not shown) of the station network module  24  or one of the PCAU suites  50 . The station network module  24  or the originating PCAU suite  50  encodes and/or compresses the audio signal and places it on multiple channels of the transmission medium  16 . The applied audio signal may be digitally encoded in the AES3 digital format, or analog format. Further, the transmitter network module  30  or destination PCAU suite  50  decodes and/or decompresses the signal, and provides the audio signal in either AES3 digital or analog format. 
     As discussed above, the media transmission system  10  may include a redundant transmission medium  16  including a primary transmission line  28  and a secondary transmission line  29 . The media transmission system  10  may be configured to retrieve backup media programming in the event of the station network module  24  and/or the transmitter network module  30  fails, or a failure of one of the transmission lines  28 ,  29 . 
     As shown in  FIG. 5  and  FIG. 6 , a radio station can have three program sources. The Main Program is the audio material heard on a standard audio channel, received on conventional radio receivers. HD2 and HD3 are alternate programs that are sent over the additional channels provided by HD Radio. A customer with a standard radio receiver only hears the Main Program. A customer with an HD Radio receiver can hear any of the three audio programs. Each program source has associated data. The data may include song titles, radio station identification, weather, and other low bit rate information. This data is referred to as Radio Broadcast Data System (RBDS, or just RDS) and normally is received simultaneously with the audio program. The Main Program information is frequently processed by studio equipment to normalize the audio levels, and possibly equalize it to produce some desired effect. The processed audio is passed as either a 600-ohm, balanced analog signal, or a 110-ohm balanced digital AES3 signal, to the PCAU suite  50  in  FIG. 5  The PCAU suite  50  in  FIG. 5  compresses the signal using Enhanced apt-X® compression, for example, to achieve a 4:1 reduction in bit rate. The compressed data is sent over multiple channels in the T1/E1 circuit  16 . 
     Channels HD2 and HD3 are similarly processed by studio equipment. In addition, they are digitized and highly compressed. The resultant bit streams are normally provided on an Ethernet 10/100 Base-T connection. These bit streams arrive at the PCAU suite  50  in  FIG. 5  and are combined with any extra customer traffic provided at the second Ethernet port. The data is sent over six of the timeslots of the T1/E1 circuit. HD2 and HD3 traffic has priority over other Ethernet traffic. The prioritization is accomplished by connecting the HD2 and HD3 traffic via port 0, and low priority traffic via port 1. The RBDS data is presented to the PCAU suite 50 as a 9600 bps data stream in RS232 format. This data is multiplexed with the compressed audio information and sent to the far end (e.g., PCAU suite  50  in  FIG. 6 ) over the dedicated Main Program timeslots. 
       FIG. 7  depicts an exemplary embodiment of an AM media station. Specifically, the lower audio bandwidth requirement allows remaining factional T1 resource to be used for other purposes such as PBX.  FIG. 8  depicts an exemplary embodiment of an AM transmitter station, which is similar to the FM transmitter station shown in  FIG. 6 .  FIG. 9  depicts an alternative exemplary embodiment of a media transmission system  10  showing the operation of a transmitter station  14  if a connection fault between the media station  12  and the transmitter station  14  occurs. Lastly,  FIG. 10  depicts an exemplary embodiment of a media transmission system  10  including two AM stations with the same ownership, but separate media programming provided from two different locations. 
     Although exemplary embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions, and substitutions are possible, without departing from the scope of the present invention. Therefore, the present invention is not limited to the above-described embodiments, but is defined by the following claims, along with their full scope of equivalents.