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D&R Eases Telephone-based Remotes
By Alan R. Peterson,
POTS-type phone boxes are for more than news gathering and high school football games. When there is a once-only chance to get a live interview with a pop music star who is in town for one show, POTS (plain-old telephone service) remains a dependable choice.
It may sound telephonic, but it gets audio where you need it fast. When production is waiting for the sound bite of an artist's voice for a promotion that has to air immediately, a unit like the Teleporter 2 from the Dutch company D&R Electronica b.v. can get audio back to the studio right away.
And it does so without having to provide a drop of power.
The self-powered Teleporter 2 has no batteries, no plug-in power supply and does not need an adapter to fit into the lighter socket of the OB van. It pulls all the energy it needs right from the phone line, which is enough to run the mixer and power a set of headphones. Finally, a remote POTS mixer that cuts the cord to the wall-wart power supply.
The Teleporter 2 was intended to be a field news gathering device, but it works fine in the sports broadcast booth as well. The Teleporter 2 is a good-sounding, easy-to understand mixer/telephone box with a number of features both play-by-play announcers and reporters will appreciate.
The idea of a self-powered telephone device is by no means novel. After all, with the exception of cellular and cordless units, telephones themselves are self powered. Those that require batteries do so only to keep the autodial memory alive.
However, the notion that you can run a remote mixer without having to find an AC source is an appealing one. Wall-wart power supplies can break at the least convenient of times. AC cords are easily lost, forgotten or get surreptitiously borrowed from the remote kit at the worst of moments.
Normal quiescent voltage on analog telephone lines is -48V DC, although this value can swing appreciably. Still, this is ample voltage to power the DTMF (Touch-Tone) dialing circuit of the Teleporter 2 and low-current chips, which were designed specifically for telecommunications applications.
Headphones can require significant amounts of power, but newer, more efficient units have fairly reasonable appetites. I found- that a basic set of department store-grade Sony headphones worked just fine with the Teleporter 2.
Low-power, high quality
I opened the unit to examine the circuit board, half expecting to find a huge 1 Farad memory capacitor inside. One would hold some reserve DC voltage and release it during peak audio demands, like when the headphones are put to full volume or the mic is yelled into.
Instead I found only straightforward low-power components and a few high quality Jensen isolation transformers. The Teleporter 2 makes it all happen with cleverly designed low-draw analog circuitry. The transformers float the grounds of the plug-in gear so hum is stopped before it gets on the phone line.
A slide switch on the panel allows tone or pulse dialing from the Teleporter
2. It is hard to imagine pulse-only Telco circuits anymore, but you would be surprised what you run into when you need a phone line badly enough. It is good to have both functions.
A nice chunky limiter inside the Teleporter 2 keeps line send levels tame. During my tests, I turned the mic input up to full and worked the mic very closely. My headphone signal sounded hot and a little clippy, but a recording made at the other end of the line sounded clean and loud. The thing works!
The Teleporter 2 has inputs for only one mic and a line-level device. If you wanted to use the unit for a two-person, two - microphone broadcast, you may want to look at other devices. Certainly an external mixer with additional mic inputs can be connected to the Teleporter 2, but that requires power and defeats the intent of going out into the field sans batteries.
Still, if you are venturing out with a recording device as well, batteries will be making the trip with you anyway. It is your decision to make.
Those "rack ears" on the front are deceptive. In the photo they look as if that is how the unit is grabbed and handled. In real life, the box is much smaller and those ears are more like shoulder strap brackets.
I Final comment: Do not use the Teleporter 2 with a cellular phone. The circuitry of the unit requires operating voltage from a public/domestic hardwired phone connection, You will not be getting that kind of sustained power anytime soon from a cellular battery.
Hang up, please
Someday, all telephone lines everywhere will be fast enough to handle digital POTS codecs without difficulty, Someday also, cellular service will be available in the remotest corners imaginable. But, until then, if your project can tolerate the limited bandwidth of telephonic audio, a unit like the D&R Teleporter 2 can mix and send satisfactory audio to the station.
Doing it without batteries is a pretty cool trick.
For information on the Teleporter-2 contact
Duco de Rijk in the Netherlands at
Telephone: +31-294 418014,