Systems Digital Audio Tranceiver/Mixer User's Manual

4-12 AUDIO OPERATIONS

Normally both LOCK LEDs work together. If the receive mode is G.722, however, they’ll

operate independently to indicate the status of individual channels.

Analog (G.711) phone calls

ZephyrExpress can send or receive standard analog (or POTS

) calls on either ISDN line,

eliminating the need for a separate telephone and analog circuit at the remote site. The

call is carried as ISDN data to the telephone company’s switching office, where it’s

converted and treated as a standard connection.

¥ Station engineers can call the remote site before establishing a high-quality

connection, to verify coding methods and bitrates.

¥ A studio producer can talk to the remote engineer while a mono broadcast is in

progress, to relay cues and other information. The call can be routed to the talent’s

headset, or just to the engineer.

ISDN TIP!

Since telcos usually charge less for a standard voice connection, using G.711 for

talkback and cues can cut the cost of remote broadcasts.

¥ Late-running talent, stuck in traffic, can call the remote site’s ISDN number from

their cellphones to alleviate panic.

Only one POTS call is possible at a time.

Analog call signal routing

The G.711 codec connects to either the Channel A or Channel B send and receive busses,

depending on which ISDN line is used for the call. Normal microphones, headsets,

routing switches, and level controls are used just as if the call were an ISDN broadcast. Of

course, audio quality is limited by the analog phone system.

Incoming POTS audio is also routed to ZephyrExpress’ internal speaker, so you can hear

that a call is in progress even if you’re not wearing headphones. The speaker level is

controllable by the System menu’s POTS volume setting, and it can be turned off by

selecting 0% as the setting.

Since G.711 bypasses ZephyrExpress’ main digital signal processing, analog telephone

levels are not displayed on the RECEIVE meter.

Receiving calls

ZephyrExpress automatically switches to G.711 mode when a POTS call comes in on

either ISDN line. All the caller has to do is dial one of the lines’ directory numbers, with

any access or area codes they’d normally use for a phone call.

When a call is received, ZephyrExpress picks up on the first ring. The internal speaker

chirps once, and the call timer for that line starts counting. If the POTS volume is turned

The acronym stands for Plain Old Telephone Service. We didn’t make it up.