User's Manual

TX PL Self-Clearing
As part of the multi-unit resolution prioritization algorithm, TX PL Self-Clearing
operates by adding the VRS transmit PL to the list of PLs that the VRS monitors. If a
VRS transmit PL is detected by a priority VRS (delay state 0), it will indicate that another
VRS is transmitting. This feature will cause the original priority VRS to count up to delay
state 1, 2, or 3, and allow the transmitting VRS to remain in priority. The delay state is
randomized to prevent multiple units from stacking up in delay state 1. In order to
prevent ICM transmissions from other VRS units affecting the priority states, the TX PL
Self-Clearing feature only works when detecting TX PL from a VRS that is repeating a
Base-To-Portable transmission. This function is not programmable, but has no effect
unless TX PL is used. This feature will not operate properly unless all VRS units are
programmed to transmit with the same frequency PL, and the receiver squelch of the
VRS750 units is set to approximately -110dBm.
NOTE: The VRS750 ships from the factory with a receiver squelch setting of
approximately -110dBm. If the VRS750 is not going to be programmed with a TX PL,
then the Global Tuner can be used to loosen the receiver squelch for better radio
performance.
ICM Functions
The in-car-monitor (ICM) allows limited use of the mobile while the VRS is enabled.
<ICM Base> Mode
In this mode pressing the mobile's PTT will cause the mobile to transmit on the mode
shown on the control head display. The VRS will not transmit the mic audio to the
portable. During portable-to-base repeat operations pressing the mobile's PTT will result
in the talk prohibit tone sounding momentarily and the mic audio will not be transmitted
to the portable. When the mic is on HUB portable transmissions will not be heard at the
mobile's speaker. When the mic is off HUB only portable transmissions with the proper
PL will unmute the speaker. The following paragraphs detail how the VRS should
operate in <ICM Base> mode during different cases.
1. No VRS repeat operations in progress and the mobile user initiates a PTT.
• The mobile will key up and transmit mic audio to the base.
• Mic-Hi line audio is not routed to the VRS transmitter.
2. During a portable-to-base repeat operation, the mobile user initiates a mic PTT.
• A momentary talk prohibit tone will be heard and the mic audio will be
disabled.
3. During a base-to-portable repeat operation, the mobile user initiates a mic PTT.
• The base-to-portable repeat operation will be interrupted.
• Mic-Hi line audio is not routed to the VRS transmitter.
• The mobile will key up and transmit mic audio to the base.
• When the mobile mic PTT is released, the base-to-portable repeat will
continue if the mobile is still receiving a base transmission.
<ICM Both> Mode