Field Report: Telos Systems Series 2101

The Telos 2101 is an on-air telephone system that uses ISDN PRI (Primary Rate Interface) lines instead of traditional POTS (plain old telephone service) lines. The system can access one to four PRI circuits for a maximum of 92 callers. ISDN PRI is related to the more commonly known ISDN BRI (Basic Rate Interface), but has a higher capacity. A BRI has two bearer (B) channels capable of carrying 64kb/s and one data (D) channel, capable of carrying 16kb/s. A BRI is sometimes called a 2B+D service. A PRI circuit contains 23 bearer channels and one data channel.

By using a PRI instead of discrete POTS lines, the last link from the telephone company Central Office to the studios stay digital, which improves audio performance. In many cases, a single PRI is cheaper than 23 POTS lines.

The system consists of three key pieces of hardware: the 2101 hub, the studio I/O (SIO) hybrid and the Desktop Director. To interface with the PRI, an installation also needs an ISDN PRI CSU and a 10/100 Ethernet switch.

The 2101 is designed for use in a facility with multiple radio stations that wants the flexibility of adding and subtracting on-air phone lines on a show-to-show or even minute-by-minute basis.

Into service

The 2101 hardware is installed in an area common to all the studios, or at least accessible via CAT-5 cabling to the studios. In our installation, we installed the 2101 hub and SIO hybrids in the engineering technical operations center (TOC). This simplified installation, but it also allows us to maintain the system without interruption to the on-air studio. This location has added benefit for us because the console/router input and output frames are also located in the engineering TOC.

Performance at a glance
Up to 32 studios
As many as 92 telephone callers
Up to 24 lines in a single studio
Uses ISDN PRI connectivity
Remotely programmable

The ISDN PRI lines from the telephone company first connect to a CSU, which then is plugged into the 2101 hub. The output ports of the 2101 connect to each of the SIO hybrids with CAT-5 jumpers. These jumpers carry the actual telephone line audio. The 2101 hub and the SIO hybrids have Ethernet cards that connect to the ports of an Ethernet switch. The Ethernet data on the switch carries all of the control information to and from the hub and SIO. It also gives access to the 2101 for programming and call-screening software. One or more Desktop Directors are installed, which connect to the SIO. Users familiar with the Telos Two√ó12 system will notice that the SIO has a similar look and feel. Each SIO and the 2101 hub is assigned a unique IP address for programming from a PC.

Programming the 2101 is where the user realizes the power of the system, because he can create a different profile (called shows) for each station and daypart. When adding shows, the user has the ability to have the same number appear on multiple studio hybrids, if he needs a common line in several locations. The system can be programmed to create a virtual rollover sequence if needed. Settings can be recalled easily. For example, if a contest is being held, the lead contest line can appear 12 times on the desktop director. Once the contest is over, the operator can change the show (profile) by selecting a new one from the desktop director.


Because the 2101 has a network card, assigning it an address on a facility's LAN makes it accessible through the LAN. Programming is then accomplished over the LAN with a utility program supplied with the software. Changes can be made from anywhere that there is access to the facility's LAN. Once installed, I made most of the changes on the Chicago system from out of the market.

While I handled most of the initial set up, the Chicago market engineering manager, Bob Fukuda, has taken over the programming. He learned his way around after a few minutes watching me set up a couple of lines. Once you understand the concept of the system, the learning curve is minimal.

The 2101 is based on a PC platform so upgrades to the hardware are easily done via Ethernet. The 2101 can be expanded to handle up to 32 SIOs. As many as 24 lines can be tied to a single extended Desktop Director for stations that run lots of contests or talk shows that need lots of lines.

Making the choice

For the Clear Channel stations in Chicago where the 2101 was installed, we were attracted to the system's ability to interface to a PRI service. As is the case in most metropolitan areas, the local telephone company was eager to offer incentives to using digital services. These services save the telephone company on its copper-pair resources. In addition, the capability of dynamically changing the complement of available lines to different stations and studios will be used frequently. Just as our console and router system allows us to access of any source to any destination, the telephone system is capable of the same flexibility.

If I could change anything, it would be the software user interface. It is not user-friendly and requires a clear understanding of its operation. Telos is currently developing a browser-based interface, which will eliminate the need to use the programming software.

Telos Systems

Another item that is being corrected is the audio level control. Because the caller audio is so clean, staying in the digital domain all the way through, the caller level needs some aggressive AGC. The current AGC is not sufficient for our use in Chicago, but again, Telos is aware of this and plans to increase the AGC capability in the next software revision for the SIO.

There are three manuals provided with the system. They are written in the traditional Telos fashion; straight to the point and thorough. I personally like the Telos manual style and these did not disappoint.

Service on the components of the 2101 is much like most of the other new Telos products. In most cases, in the event of an SIO problem you will probably send the unit to Telos for repair. The hub is a PC and could be maintained on-site. The call directors are terminals, which could also be serviced in the field if necessary.

Mettler is regional engineering services manager for Clear Channel Radio. He is based in Indianapolis.

Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.

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