System Feature Overview 23
68007024085 April 2011
2.2.3.5 Polite or Impolite, or Voice Interrupt While Participating in a Call (In
Call Criteria)
The In Call Criteria applies only when the radio is participating in an active call. The radio can
optionally allow others that are part of the call to transmit impolitely (Always), to automatically clear
the channel using the Voice Interrupt feature prior to beginning the voice transmission (Voice
Interrupt), or to follow the previously configured channel access (Follow Admit Criteria). If
configured for an In Call Criteria of Always, the user will receive a Talk Permit Tone when they
press the PTT while receiving a transmission for them. In other words, a radio has the ability to
transmit over another user while listening to their transmission. However, when this happens, the
other party does not stop transmitting and therefore RF contention can occur which may corrupt
both transmissions. The In Call Criteria of Voice Interrupt is an alternative to the In Call Criteria of
Impolite.
The Voice Interrupt option has advantages including the ability to avoid the previously described
RF contention issue by clearing the channel prior to beginning a transmission, which yields a
higher probability of successfully communicating with the intended target radio(s), as compared
with the RF contention encountered with impolite transmissions. However, Voice Interrupt has
disadvantages including a longer channel access time when an interruption is necessary, due to
the signaling having to complete the interruption and handoff.
If configured for an In Call Criteria of Voice Interrupt, the radio user receives a Talk Permit Tone
when PTT is pressed while receiving an interruptible voice transmission and the channel is
successfully cleared down. In other words, a radio user has the ability to clear the channel of
another user’s interruptible voice transmission before beginning their own voice transmission
when both radios are participating in the same voice call (e.g., both are members of the same
group during a Group Call, or both are participating in the same Individual Call). The radio user
whose transmission was interrupted, receives a Talk Prohibit Tone until the user releases the PTT.
If the channel is not successfully cleared down, the user typically receives a Channel Busy Tone
until the PTT is released.
NOTE: For the Voice Interrupt feature to operate consistently, all radios using the channel should
be provisioned with the ability to be interrupted. However, not all need to be provisioned
with the Voice Interrupt capability.
If some radios are provisioned without the ability to be interrupted (e.g., normally desirable for a
supervisor’s radio), then those transmissions cannot be interrupted and the radio user receives a
Channel Busy tone if the Voice Interrupt feature is attempted while receiving an uninterruptible
voice transmission.
If configured for Follow Admit Criteria and the previously configured channel access (Admit
Criteria) is set to either Channel Free or Color Code Free, the user will receive a Transmit Denial
Tone when they press the PTT while receiving a transmission for them. Users must wait until the
user stops transmitting and call hangtime starts before they are granted a transmission. Utilizing
the Channel Free Tone helps train users from transmitting too early. Although a setting of Always
may be useful for speeding up conversations for well disciplined users, it may cause undisciplined
users to “step over” other users. Therefore, it is recommended that most users are provisioned
with an In Call Criteria of Follow Admit Criteria.
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