CTI Products TSAM Transmitter Steering & Audio Matrix - Manual (Page 19)

TSAM Installation and Maintenance Rev. 2.10 Chapter 2
CTI Products, Inc. Main Channel Operation
11
2.5.1 Repeater Operation with various Steering Algorithms
The steering update mode used determines how repeater keying takes place in the TSAM. The TSAM
uses Instant and End of Receive Update modes. The Smart-Steer
 algorithm always uses the EOR update
mode. First RX steering uses either Instant update or EOR update modes. Repeater keying in each of
these modes is described in the following sections.
2.5.1.1 Repeater Keying with Instant Update Mode
For repeater mode operation, the TSAM will key the steered transmitter when the Free Vote time period
expires. The Free Vote time starts running the instant vote activity is detected on the TSAM inputs.
If the TSAM is in instant update mode, the proper site is steered just before the keying starts. Console 1
TX audio is then routed to the steered site. Repeat audio from the comparator must be routed to the C1
TX audio port. This is accomplished by taking the repeat audio output of a comparator with console
priority capability, or by means of an external relay which will switch between repeat and console audio.
One disadvantage of instant update keying is that the repeater transmitter is not keyed until after the Free
Vote timer expires. If Free Vote is set to a high value, to give the comparator time to make a better voting
decision, the initial part of a transmission will not be repeated. Care must be taken when setting Free Vote
to balance steering performance with system access time. Only repeat audio is effected by Free Vote.
Console audio is not cut off by Free Vote.
2.5.1.2 Repeater Keying with EOR Update Mode
In this mode, new vote activity is repeated over the last used transmitter site (a new site is not immediately
steered). Repeater keying is initiated at the time Free Vote expires. With EOR Update mode, Free Vote
can be set very short or to 0 msec with no degradation of steering performance. This is because the
steering decision is made at the end of vote activity (not at the beginning). After EOR, a steering decision
is made and the new TX site is steered. The next voted signal is then repeated on this site.
2.5.2 Repeater Hang Time
Repeater Hang Time is used on conventional repeater systems to improve system access time. During
hang time, the repeater transmitter remains keyed. Subsequent transmissions due not incur the delays
encountered when re-keying the repeater transmitter. These delays consist of 160ms typical tone keying
delay, and 200ms typical PL decode delay for the receiving field radio.
In a transmitter steering system, the repeater transmitter may change sites on each retransmission, requiring
that a new transmitter be keyed each time. This makes it more difficult to provide the same quick access
of a single transmitter repeater system.
To minimize system access the TSAM uses the following system hang time algorithm.
2.5.2.1 Repeater Hang Time with Instant Update Mode
In Instant Update Mode, when repeat traffic ends, the TSAM keeps the current system transmitter keyed.
When the next transmission begins, the TSAM steers to the site for that transmission. If no site change
occurred, the transmission can proceed over the current transmitter that is still keyed due to system hang
time. In this case, system access time is reduced. If a site change is required to repeat the next
transmission, then the TSAM unkeys the current site and keys the new site. In this case, additional system
access time is added for a new site key-up and PL decoding in the field radio.