24 System Feature Overview
2.2.3.3 Polite to Own Digital System Operation
(Admit Criteria of “Color Code Free”)
This criteria applies only to digital channels. When configured for Polite to Own Digital System
operation, the radio checks for an idle or busy channel, prior to allowing a transmission. This
operation is similar to the Polite to All operation with exception that the radio is not polite to analog
systems or other system’s transmissions. It is only polite to other traffic in its own system. This
option is often used when there are no neighboring communications systems, or when there is no
concern about interfering with radios in neighboring communication systems.
2.2.3.4 Polite to Other Analog System Operation
(Admit Criteria of “Correct PL”)
This criteria applies only to analog channels. When configured for Polite to Other Analog System
operation, the radio checks for an Idle or busy channel, prior to allowing a transmission. This
operation is similar to the Polite to All operation with exception that the radio is not polite to analog
systems with the same PL. It is polite to other system’s transmissions. The radio checks for a PL
match prior to allowing a transmission.
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 Private 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.
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