Motorola PURC Tone Remote Control

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Motorola PURC Tone Remote Control
Purc signaling.png
Frequencies 470 MHz,150 MHz
Frequency Range 150 MHz - 470 MHz
Mode FM
Modulation AFSK
ACF
Bandwidth 12.5 kHz
Location United States
Short Description Motorola Paging Universal Remote Control, also known as Motorola PURC, is a way of keying on and off multiple paging transmitters in a simulcast environment by rapidly shifting AFSK modes on a single transmitter, with control tones such as MDC1200 acting as a means of "remotely controlling" the transmitter.
I/Q Raw Recording
Audio Sample

From http://www.braddye.com/purc/purc_tones.html:

"Tone Remote Control (TRC) is a Motorola control sequence used in keying transmitters. The TRC sequence comprises three basic elements: High Level Guard Tone (HLGT), Function Tone (FT), and Low Level Guard Tone (LLGT). The TRC sequence follows an audio level convention whereby FT is 10 dBThe decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, here the strength of a received signal. below HLGT and LLGT is 30 dBThe decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, here the strength of a received signal. below HLGT. The relative audio levels of HLGT, FT, and LLGT are usually referenced to a system Test Tone level. Test tone is defined as a 1000 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). signal sent from the controller at the system operating level by which the transmitters are aligned to produce nominal analog transmit deviation. Relative to Test Tone, HLGT is 5 dBThe decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, here the strength of a received signal. above Test Tone, FT is 5 dBThe decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, here the strength of a received signal. below Test tone and LLGT is 25 dBThe decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity, here the strength of a received signal. below Test tone. Figure 2 graphically illustrates the control sequence:

PURC control diagram braddye.PNG


Digital Remote Control[edit]

Digital Remote Control (DRC) is a Motorola developed MSKMinimum-Shift Keying (When Shift/Bd = 0.5. It is impossible to get this ratio to be lower than 0.5, hence it is called the 'Minimum' shift.), Minimum Shift Keying, communications control scheme. The digital signaling scheme uses Cyclical Redundancy Checking (CRC) and convolutional coding. This provides excellent error detection and forward error correction in the presence of fading, noise, and multi-path distortion in the outbound (control) and inbound (diagnostic) RFRadio Frequency channel. The code was developed by the Motorola Data Communications group and therefore it is referred to as MDC. The signaling scheme used for Paging DRC control is a 1200 baudBaud (unit symbol Bd) is the unit for symbol rate or modulation rate in symbols per second. scheme, MDC 1200. The signaling scheme is transmitted via 1200 and 1800 HzHertz (Hz), unit of frequency, defined as one cycle per second (1 Hz). modem tones for distribution through phone line and RFRadio Frequency mediums. An MDC 1200 message used for paging control is approximately 233 milliseconds in duration.

Unlike TRC, which had limited control functionality, DRC is able to transfer much more information in each transmitted packet of MDC 1200. Due to error detection and correction, DRC offers substantially improved performance reliability over TRC in noise environments. Unlike TRC, which relied on "pauses" and "gaps" of silence to force mode switches, DRC simply sends a specific message identifying the desired mode of operation. DRC is therefore referred to as a positive control scheme. See Figure 3 and 4 below, which illustrate Analog and Binary DRC keying sequences. The sequences shown are for single key and dekey modes. If multiple and alternating key requests were present the dekey message would be substituted with the appropriate MDC keying message. HLGT does not need to be present since the link will remain keyed on activity.

DRC.PNG

Advanced DRC.PNG