Raytheon SNV-12, Installation And Operation Manual

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SNV-12 Operations Manual
3-76
When the filter is disabled, the SVM does not run its DSP notch filter algorithm even when set
for Pilot Tone COR. The SVM cannot squelch until it detects a pilot tone, and some time is
required to detect this tone, so it will be momentarily present in the voted audio output (and,
when Repeat Mode is used, in the retransmitted voted audio). This momentary bit of pilot tone
will be heard at the end of each voting sequence. As soon as the pilot tone is detected in all
sites, the voting sequence is ended and the voted audio output is muted.
( *Note that for the encrypted audio example given above: the SVM measures noise from 2300
to 3k Hz. The SVM expects that there is mostly noise only at these frequencies, with most
speech components from 300 to 800 Hz. If the encryption mode inserts speech energy into the
2300 to 3k Hz range, the voting algorithm may be affected. If poor voting performance is
noticed, it may be helpful to use COR Lock. In this mode, the voter makes a quick initial vote
and holds it until all sites squelch. This initial vote usually occurs before speech is present in
the RX input.)
Table 3-68 Pilot Tone Notch Filter
SW5-2 Pilot Tone Notch Filter
OFF Enabled *
ON Disabled (no notch)
Note: To Disable with the SVM-1 Module, strap terminal block pin 10 to a
ground pin for each SVM-1 that will use this feature. For SVM-2
modules, this rear panel terminal serves a different function so the
dipswitch must be used.
SW5-3 Term Block Pin 19 Configuration – Unsquelch Inhibit
This switch enables an extra feature at the Rear Panel Terminal Block (TB1-12) Pin 19.
Normally this pin provides a TX Inhibit input, which disables the TX outputs (TX audio and
PTT signals) whenever it is pulled low. This is the only functionality that this pin has for the
SVM-1. When SW5-3 is switched to on, for SVM-2 modules, pin 19 is configured as an
Unsquelch Inhibit Input. This means that, whenever pin 19 is pulled low, the associated SVM
will not declare itself unsquelched for any reason and therefore it will not become eligible for
voting, line fault, etc.
Table 3-69 Pin 19 Configuration
SW5-3 Term Block Pin 19 Input
OFF Transmit Inhibit *
ON Unsquelch Inhibit