MTEL Simulcast Systems

MTEL has been manufacturing simulcast products for over 20 years. Most have been deployed as wide area networks for emergency service organisations. All the equipment are “bolt on” products to existing transmitters and CAD servers. The simulcast equipment provides commercial grade POCSAG encoding for the pagers and ensures the integrity of the data being transmitted is within the specifications required for successful simulcast transmission.

MTEL now have adapted the wide area designs to operate in a smaller campus wide network.

MTEL has developed products which will take inputs from CAD servers in the form of TCP and serial inputs. Converts the message packets into a POCSAG data stream and transmits the information to one or more transmitter sites using analog channels such as building block cabling to the transmission equipment. The transmission equipment contains MTEL products which then convert the analog messaging back into digital signals suitable for a paging transmitter.

This technique provides the transmission system with the ability to

•        Transmit pager information to multiple transmission equipment simultaneously.

•        The ability to synchronise transmission equipment.

•        The ability to add transmission equipment without interrupting the existing system.

•        Control the transmitter equipment.

•        Perform testing on a live network.

•        Ability to combine multiple inputs from many message servers.

•        Separate the transmitter equipment from encoder and server equipment.

•        Use existing analog building block cabling equipment typically used for telephony.

 

MTEL Simulcast Products

The PC2095 is a new fourth generation of MTEL POCSAG products.

Developed in 2018 to replace a growing demand in internal paging systems, this current POCSAG device is capable of being configured to do different functions in the simulcast environment.

The PC2095 can be configured as a

1. POCSAG Encoder
2. Transmitter Controller
3. Network Controller
4. POCSAG Decoder

The PC2095 was specifically developed for campus wide networks and has multiple functional elements which can be added and removed to change the device operation. It contains core elements for all devices such as AC power supply, daughter board computer module, and isolated DC supplies.

It has evolved from the PC2080 POCSAG Encoder which was designed to operate directly with a local paging transmitter over short distances of single metres.

The PC2090 was developed to add analog capability to the PC2080 design. This allows the encoder to be located hundreds of meters apart from the transmitter using analog lines.

The PC2095 combines all the functionality of the PC2080, PC2090 and has additional functionality to transmit messages to multiple sites simultaneously using analog transmission. The PC2095 also has TCP interlocking between dual PC2095 devices to allow each device to share the transmission system.

 

1        MTEL PC2095 POCSAG Functions

The PC2095 has the following capabilities of the PC2090;

•        Continuous Encoding at 512 and 1200 bps.

•        Batching messages on the same baud rate.

•        Simultaneous Batching and transmission.

•        Priority Message Insertion.

•        TCP Packet buffering.

•        Dual Frequency Transmitter Control.

•        Opto-isolated PTT and Baseband.

•        Bell 202 Modem analog outputs.

 The PC2095 has the additional features;

•        Digital transmission control of transmitter.

•        Batch specific transmission control.

•        Embedded message transmission control.

•        4 analog outputs.

•        2 analog inputs.

•        Transmission control monitor processor.

•        TCP Interlocking between dual PC2095 devices.

 

1.1       PC2095 Functional Block Diagram

 

 

The PC2095 contains multiple functional elements which can be coupled together to provide specific functionality at both the encoder and transmitter ends.

All inputs and outputs are isolated as is the analog and digital circuitry. This provides the device with very high noise immunity when operating in high RF environment. 

On the input side there is two TCP devices which are configured to take messages from a server and inter-server handshaking.

There is also two analog inputs to allow the device to receive modem data from two sources.

The outputs are digital and analog. The POCSAG code and transmitter control are delivered by an 8 bit DAC which provides very precise BELL 202 modem data as well as the ability to send PURC control tones. The digital outputs can be open collector or TTL compatibility. 

The ZWorld processor module can be configured as an encoder and transmitter controller. The transmission control is embedded into the start of every data stream and the ZWorld processor firmware can be configured to encode or decode the data stream. 

The ZWorld processor module can also be configured as a transmitter station control device where it decodes the transmission stream at the start of all the data streams. This is useful for maintenance purposes where maintenance teams are monitoring the effective radio footprint of a single site or a combination of sites.

This processor also provides bit error on the data stream and full decoding of the POCSAG data. This information can be accessed through the TCP port onboard diagnostics menu.

The POCSAG data stream in the station control mode can use either a direct conversion of the analog data into digital data via the PLL or it can alternatively use the encoder circuitry to re-clock the data stream. This occurs where the analog levels are very low creating unacceptable digital jitter in the PLL.

 

1.2       PC2095 configured as a Simulcast Encoder

  

 

The computer module performs most of the functionality in this system. It takes the TMP packets from the pager server and queues the messages. The queue provides priority insertion so that as a priority message is received it can jump the queue. The queues are then built on the fly to the POCSAG buffers. These buffers are POCSAG encoded memory next in line for a transmission. The buffers are clocked out based on several rules and a batch is created on the fly. 

The digital output is passed directly to a DAC which allows the modem CPU to produce industry standard PURC tones or the Bell 202 standard tones for digital paging data. 

The analog stream is feed to 4 audio outputs giving the capability of 4 simulcast transmitter sites. Importantly sites can be added and removed without disturbing or interrupting the existing encoder operation. The 4 outputs are wired to the rear of the unit and are individually routed to the block cabling.

 

1.3       PC2095 Testing Functions

One of the most difficult tasks for maintenance personnel is to test a live system without impacting the service. The PC2095 has two functions which improve testing; priority messaging and transmitter control. Live data always has priority over testing data. Disabling the transmitters to measure the impact of individual sites. 

The encoder can select or deselect any combination of the sites through the pager server interface. The PC2095 device has preconfigured pager numbers which can be used to send messages to single transmitter or any combination. This means the pager server does not have to be changed to implement testing. 

This is most useful when the maintenance staff are trying to locate pager coverage anomalies. They can cycle test on the live system as the live data will always have priority. 

Testing can reveal coverage issues as shown in the diagram below.

It can identify the lack of coverage in the basement of Building E, or simulcast timing in the overlap areas in Building B, C and D. It can identify that the simulcast has improved the coverage in Building C as the signal arrives from two different directions.

 

 

2        MTEL PC2095 Simulcast Transmitter Controller

 

The PC2095 has several new functional elements which allow the device to be completely reconfigured to operate as the transmitter end point controller. 

In this case it will take analog data from two ports and combine them into a digital reconstruction of the original POCSAG data stream. The two input ports provides connection to dual encoders running in parallel or hot standby operation. 

The processor monitors the analog data stream and controls the PTT to the transmitter. In this way the transmitter is controlled using in-band signaling which can change at the batch level.

2.1     PC2095 configured as a Simulcast Transmitter Controller

 

 

 

 

 

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Last modified: 01-Jun-2022