Raytheon SNV-12, Инструкция по установке и эксплуатации

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SNV-12 Operations Manual
7-1
7 Options
There is one option presently available for use with the SNV-12 Voter:
7.1 PTG-10 Pilot Tone Generator
In an LMR voting system, receivers are strategically placed around a geographic area (at voting
sites) to fill in dead spots where portable radios can‟t normally be heard by other portables, by
the repeater, or by the dispatcher. The audio from each receiver is linked to the voter, which
continuously compares the signal from all receivers while passing through the best quality
signal to the dispatcher or to the local repeater. In this way, any portable in the voting area can
be heard by the dispatcher, or by any other portable through the local repeater. In this system,
it is necessary to transfer a receiver's COR or COS (Carrier Operated Relay or Carrier Operated
Squelch) signal to the voter from a remote receiver site.
The PTG-10 Pilot Tone Generator Module produces a controlled pilot tone as a means of
transferring this COR signal over the same path as the receive audio, eliminating the need for a
second communications path for the COR signal. Audio output exits a receiver through one
pair of wires and the COR (a DC logic signal) exits the receiver on another wire. The PTG-10
injects a pilot tone on the audio line whenever the associated receiver is squelched, and
removes the tone whenever the receiver is unsquelched.
When a voting receiver detects a carrier (receives a signal), it unsquelches and issues a COR
signal to the PTG-10. When the PTG-10 receives a COR signal the tone is removed from the
audio link and the receiver audio is passed through the link to the voter.
The pilot tone also functions as a line proving tone: The removal of the pilot tone on the link
notifies the voter to expect speech signals from the voting receiver. If the voter doesn't sense
speech within a programmed time, it faults that particular voting site on the assumption that
either the voting receiver is not functioning, or the link is broken between the voting site and
the voter. The SNV-12 disallows use of that voting input until voice is received from the distant
receiver or until the pilot tone returns.
The PTG-10 is capable of injecting one of two user selectable pilot tones: 1950Hz or 2175Hz.
The module is 6.84" x 2.42" x 1.2" and is enclosed in a metal box suitable for mounting to flat
surface or to a standard 19" rack. The mounting tabs are designed so that bolting three units
together will span the standard 19" size rack. Wiring makes system interconnections to a
screwdriver type terminal block. Audio input from the receiver is unbalanced, while audio
output to the voter is configured for 600 Ohm balanced operation. The terminal block has
provisions for a COR input (either positive or negative logic), power input (+11 to +15 VDC)
and ground. Two LEDs are provided: One indicates the state of the receiver's COR signal and
one is a power indicator. The overall audio level is adjustable with an independent adjustment
to set the relative pilot tone level..