3.4.8.3
Once the telephone and radio party have both been contacted, the operator should advise the telephone party that a phone patch is being set up. He may want to advise that a short noise burst (not extremely loud) will be heard in the telephone receiver, and that the conversation can proceed following the burst. The operator then pushes the TEL LINE/RADIO button to begin adaptation, indicated by a flashing TEL LINE/RADIO LED.
3.4.8.4
After the RTU-292 automatically adapts itself to the phone line, and the TEL LINE/RADIO LED will stop flashing and stay continuously illuminated. This indicates that a complete link has been established between the distant radio set and the distant telephone, via the RTU-292 and the local radio set.
3.4.8.5
Progress of the call may be monitored via the speaker on the RTU-292 front using the SPEAKER/PHONE and SPEAKER/RADIO buttons.
3.4.8.6
The call may also be monitored with the handset. The operator may speak and listen to either the telephone party alone, the radio party alone, or both together, using the HANDSET pushbuttons.
3.4.8.7
When the conversation is complete, the operator pushes the TEL LINE OFF button to disconnect from the phone line. The TEL LINE/RADIO and TEL LINE/PHONE LEDs will both turn off, indicating that the phone is back on-hook (disconnected).
3.4.9 TRANSMITTER KEYING, HALF DUPLEX SYSTEM
For a normal half-duplex radio link, it is usual for the VOX in the RTU-292 to key the transmitter. The VOX responds to signals from the telephone line and operates the keying circuits when voice is present. Once the VOX has tripped, it remains active for the selected “hang time” following the loss of audio to prevent dropout on pauses between syllables. The unit also incorporates a short delay of the transmitted audio, which allows the VOX to key the transmitter a short time before the audio arrives, so that the RF output can be at full power to avoid missing part of the first syllable.
The VOX in the RTU-292 is generated within the DSP and is extremely sensitive and reliable. However, there are occasions when the audio level from the telephone line is too low to operate the VOX reliably, or for some other reason it is desired to key the transmitter manually. To do this, operate the front panel KEY pushbutton or the handset PTT button to key the transmitter. The VOX switch can be left engaged, if desired, so that the operator can override the VOX at any time, or the VOX may be disengaged, so all keying occurs manually.
