JPS PTG-10, Инструкция по установке и эксплуатации, Страница: 5 / 26

PTG-10 Operations Manual
Interoperability Now!
1-1
1
General Information
1.1
Scope
This instruction manual provides the information necessary to install, operate, and maintain the
PTG-10 Pilot Tone Generator.
1.2
Description
1.2.1 General
In an LMR voting system, receivers are strategically placed throughout a geographic area (at
voting sites) to fill in dead spots where portable radios cannot 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 signals from all receivers and passes 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. COR is an indication that the
receiver has broken squelch; the voter needs this information to know which receiver site or sites
are currently unsquelched and therefore receiving a valid input signal.
The PTG-10 Pilot Tone Generator Module produces a controlled pilot tone that transfers the
COR signal from a remote receiver site to a voter. The PTG-10 transfers the COR signal over
the same path as the receive audio, eliminating the cost of a second communications path for the
COR signal. Audio output (an AC signal) exits a receiver through one pair of wires and the COR
(a DC logic signal) exits the receiver on another wire making it impossible to carry both the audio
and the COR on the same audio pair. The PTG-10 converts the COR signal to a tone which is
mixed with the audio from the receiver, removing the need for a COR line. The PTG-10 works
by injecting a pilot tone on the audio line whenever the associated receiver is squelched, and
removes the tone whenever the receiver is
un squelched. When the receiver used in the voting
application detects 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 from the PTG-10 can also function as a line proving tone to insure the integrity of
the audio link in the following way: the removal of the pilot tone on the link notifies the voter
to begin looking for voice signals from the voting receiver. If the voter doesn’t sense voice
coming from the receiver 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
receiver 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 either of two user selectable pilot tones: 1950 Hz or 2175 Hz.
The module is 6.84" x 2.42" x 1.2" and is enclosed in a metal box suitable for mounting to any
flat surface or to a standard 19" rack. The mounting tabs are designed such that bolting three
units together side by side will span the standard 19" size rack. System interconnections are