NOTES, RESOURCES, ADDITIONAL INFORMATION | 97
Application Example - WKSU
WKSU is a non-commercial FM radio station affiliated with Kent State University. It features
NPR, APM and PRI programming, classical music, regional news and, on weekends, folk music.
The station serves the Akron and Cleveland radio markets with its main FM service and six
repeaters The main FM and four full power repeaters each host four full-time HD Radio chan-
nels: a simulcast of the main service, a folk music channel, a classical service, and The WKSU
News Channel. All of the programs are also streamed for Internet listeners.
The office and studio facility is housed in a stand-alone building at the edge of the Kent State
University campus.
The two largest studios are equipped with Axia Element consoles. One of these is the main
on-air control room, while the other is used for producing a variety of long-form programs,
including an evening interview and call-in program.
The VX currently serves these two studios.
The main station call-in numbers are delivered via a SIP service offered by the VoIP provider
bandwidth.com. IP network service is from the local Telco and is delivered over a T1 circuit,
with the University’s Internet connection being a backup. A router located on the WKSU
premises is configured for automatic backup. 20 telephone numbers are delivered over the SIP
service, which may be used for both incoming and outgoing calls. Despite the leading-edge
nature of SIP Telco service, CE Chuck Poulton and network administrator Dan Kuzinsky ??
report that it has proven reliable and has delivered excellent audio quality, perhaps because
call audio is maintained 4-wire (independent send and receive audio paths) and digital from
the PSTN to the studio. The PSTN g.711 coding is maintained until it is converted to the high-
fidelity Livewire format in the VX system.
Two analog lines from the local Telco connect to the studio IP system via a Grandstream 4-line-
FXO gateway. Another two lines are brought into the gateway from the University’s NEC PBX.
An FXO interface card could have been installed into the Asterisk, but a dedicated external
device was chosen as a measure to optimize audio quality. Fortunately, the NEC PBX provides
“disconnect supervision” via a momentary break in loop current. The gateway was configured
to respond to this. (if that hadn’t been possible, the gateway would have to be configured to
respond to the return of dialtone.)
In the other direction, two dialtones are provided from the VoIP side to the Nortel PBX via a
Linksys two-line ATA (Analog terminal Adapter) – an FXS gateway that converts VoIP to analog,
including talk battery, generating ringing, etc. WKSU has a number of phones on the PBX and
this puts a couple of the VoIP numbers on phone buttons.
An Asterisk PC-based PBX is installed functionally “in front” of the VX to provide a basic
automatic answer and IVR (Interactive Voice Response) function. Callers are greeted with a
welcome message and a choice of leaving a message, going on the air, or speaking to the
receptionist. When a caller chooses the option “go on the air,” the call is passed to the VX,
where it may either be directly answered on-air or be fielded by a producer. This IVR function
is created through a web GUI for Asterisk called ‘FreePBX’
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