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A type of system known as a simplex repeater uses a single transceiver and a short-duration voice recorder, which records whatever the receiver picks up for a set length of time (usually 30 seconds or less), then plays back the recording over the transmitter on the same frequency. A common name is a "parrot" repeater.
Coded panels were the earliest type of central fire alarm control, and were made during the 1800s to the 1970s. A coded panel is similar in many ways to a modern conventional panel (described below), except each zone was connected to its own code wheel, which, depending on the way the panel was set up, would either do sets of four rounds of code until the initiating pull station was reset ...
In the mid-1960s, Simplex attempted to introduce low-voltage DC systems; these panels were not a success. Most of Simplex's audible notification appliances prior to the 1990s were relabeled Benjamin Electric, Federal Signal, Faraday, and Autocall devices. Simplex's time-division began to lose market share, but their newly founded fire alarm ...
For example, a fire department in Colorado was on a 46 MHz channel while a police department was on a 154 MHz channel, they built a cross-band repeater to allow communication between the two agencies. If one of the systems is simplex, the repeater must have logic preventing transmitter keying in both directions at the same time.
Repeater equipment: GMSK Node Adapter - these devices are hardware GMSK modems with firmware to take D-STAR protocol frames over a USB cable and provide the necessary logic and GMSK modulation to control a simplex node or a full duplex repeater. One repeater that is easily adaptable is the Kenwood TKR-820 as documented by K7VE. [27]
Simplex communication is a communication channel that sends information in one direction only. [ 3 ] The International Telecommunication Union definition is a communications channel that operates in one direction at a time, but that may be reversible; this is termed half duplex in other contexts.
This panel was the 2 zone variant of the C-series conventional fire alarm panels released by Autocall in the late 1990s. When Thorn was purchased by Tyco-owned Grinnell in 1996, their systems were branded under "Grinnell/Autocall". [5] In 2001, Tyco purchased Simplex Time Recorder Company and merged it with Grinnell, forming SimplexGrinnell. [6]
From 29.000 MHz to 29.700, The FM sub-band is usually channelized into repeater and simplex frequencies. The channels are commonly grouped into repeater inputs, simplex, and repeater output frequencies. Repeater input frequencies: 29.510, 29.520, 29.530, 29.540, 29.550, 29.560, 29.570, 29.580 and 29.590 MHz.