GAI-Tronics CB193-001 Call Boxes - Manual (Page 26)

Pub.: 43004-031E
Model CB193-xxx, CB194-xxx, and CB195-xxx RF Call Boxes Page 25 of 52
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RF Call-Box-to-Telephone Communication Protocol
In all of the use cases described in the tables below, the call can be discontinued at any time when using
the Model CB194-xxx Handset RF Call Box. If the handset is put in the on-hook position, the Call Box
searches for no channel activity and disables the PL1877A Telephone Interconnect (MRTI 2000) from
continuing the phone connection. When using Models CB193-xxx and CB195-xxx (push-button
versions), the call is discontinued following the time-out constraints programmed in the Call Box and
PL1877A.
Normal Use
Step Action Response
1 User presses and releases PTT
button (momentary) Call Box wakes from low-power sleep mode, checks transmit
channel activity and status lamp slowly flashes red to
indicate unit is operating.
2 No transmit channel activity
detected Call Box keys radio and initiates communication with
PL1877A. Status lamp continues to slowly flash red to
indicate unit is operating.
3 PL1877A detected and dials
phone number Call Box dials preprogrammed number. Status lamp slowly
flashes red to indicate unit is operating.
4 Number dialed complete Status lamp stops flashing red. Ring or busy signal is
broadcast over speaker.
5 Phone connection complete Incoming audio is broadcast over the Call Box speaker or
handset receiver and the status lamp lights steady red as a
signal to wait and listen (receive audio present).
6 User presses and holds PTT
button (maintained) Call Box keys the radio and checks transmit channel activity.
The status lamp lights red to indicate “wait” period. With no
activity detected, a “go-ahead” splash tone is heard on the
speaker or handset receiver and the status lamp lights green
as a signal to begin talking. Call Box transmits audio to
PL1877A while timing the transmit duration.
7 User releases PTT button Call Box un-keys the radio and the status lamp is off.
8 Carrier is detected by radio Incoming audio is broadcast over the Call Box speaker or
handset receiver and the status lamp lights steady red as a
signal to wait and listen (receive audio present).
9 Call Box detects a lack of PTT
or carrier detect activity for
the programmed duration The status lamp flashes red, the Call Box terminates the call
with the PL1877A, and emits three tones to the speaker. Call
Box terminates the call by powering down the radio and
audio circuitry. The status light is off and the unit returns to
its low-power sleep mode.