Guardian Telecom Inc.
Installation & Operation
TBA Models
Page 8
4.4. PTT Actions
The Central Station Push to Talk (PTT) switch has the highest priority in using PTT.
When the PTT is pressed on the Monitored or Stations #1, #2 or #3 the stations are a first-come
first-served basis for PTT.
When the PTT switch on the Monitored Station is pressed the other speakers on the system will
output a “ringing” tone for as long as the PTT is pressed.
When the PTT switch on the Central Station, Stations #1, #2 or #3 is pressed the system will use
the speaker on that station to generate audio for the other station speakers.
4.5. Alert or Go-Ahead Tone
The Talk Back Amplifier (TBA) has a tone generator that sounds similar to a telephone ringing.
This dual tone (“Ringing”) is generated for two purposes:
Alert
Go-Ahead
The Alert Tone or “Ringing” is caused by the Monitored Station pushing the Push to Talk (PTT)
switch.
The Go-Ahead short “Ringing” is a 0.1 second long sound burst that indicates to the users that a
PTT switch has just been released on the Central Station or Station #1, #2 or #3. This Go-Ahead
indicates that the other station has ceased pressing the PTT switch and that normal operation can
be resumed. When this post announcement short “Ringing” tone is heard it confirms to the listener
that the system is in the receive mode.
Jumper JP1 on the Printed Circuit Board Assembly (PCBA) is a switch to allow the injection of the
post PTT Go-Ahead or short “Ringing” tone. Moving JP1 to the bottom set of terminals will disable
the Go-Ahead or short “Ringing” tone.
4.6. Applications on Drilling Rigs
In drilling rig applications the TBA normally consists of:
Central Station at the doghouse with a speaker and microphone
Monitored Station at the monkey board
Station #1, #2 and #3 as needed.
The monkey board or racking board for the derrick man is up on the drilling rig tower, and the
derrick man’s instructions to the dog house (driller’s communication shack) should be continuously
monitored.
4.7. Applications on Shipboard
Audio monitoring of the wheelhouse or control station can be used to inform the engine room and other
stations of the actions needed to be performed. In this way commands for ship operation can be
communicated without delay by the ship operator simply speaking.
The telephone intercom on board the ship is connected to a special impedance of the Central Station
made for the 600 Ohm telephone system. A PTT from the telephone line is used to activate the output
to the talk back speakers both FORE and AFT. After the PTT the FORE and AFT can reply back to the
telephone system by talking to the speakers. The period for the FORE and AFT stations to talk back
after a PTT is received from the telephone interface is selected by a jumper on Monitored Station PTT
for 1 minute, or a jumper on Station #1 PTT for 10 minutes.
5.
Application Restrictions
The Talk Back Amplifier (TBA) enclosure is not approved for use in hazardous areas.
The Central Station console microphone (as supplied) is not approved for use in hazardous areas. A
microphone may be used in hazardous areas if it is connected through an approved intrinsically safe
barrier.
