WISCO International (Zetron - MODEL 55D Digital Repeater)

Extending the range of paging transmitter systems can be an expensive and difficult endeavor. When the loading on a paging channel is low, adding expensive simulcast transmitters is not cost effective. Zetron�s solution is the Model 55D MODEL 55D

Digital Repeater.

The Model 55D extends paging range when it is connected to a receiver and transmitter tuned to the paging channel. It sequentially decodes, stores, and rebroadcasts POCSAG paging information to fill-in areas outside the main paging transmitter�s range. The Model 55D uses the paging channel itself as a link to the remote site, eliminating the need for costly link equipment at the site. The Model 55D monitors the paging frequency to prevent transmission of pages when the frequency is already in use by another system.

APPLICATIONS

Low cost POCSAG paging fill-in repeaters for:

Hospitals and other on-site applications
Rural RCC and PCP wide-area systems
Simulcast systems beyond the link transmitter range

The Model 55D samples paging information directly from a receiver�s discriminator circuitry. When POCSAG paging data is detected, the Model 55D begins to �record� the digital paging information into a large RAM buffer. Sophisticated error-correction software eliminates noise, interference, and falsing on non-POCSAG pages as the data is stored into the buffer. When the original transmission is complete, the Model 55D closes its PTT relay and retransmits the buffered paging data.

Features

Repeat of POCSAG data on the main paging channel
Eliminates the need for separate link infrastructure
Eliminates need for costly simulcast equipment
Supports 512 and 1200 baud POCSAG
Large storage capacity - 17 minutes of 512 baud POCSAG
Optional System Identification to eliminate retransmission of unwanted pages from other paging terminals
Addressing - allows sequencing of up to 7 repeaters for wide-area coverage
Periodically transmits Morse code station identification for FCC compliance
Completely software controlled; no hardware PLLs

Power Requirements	10 - 14 VDC fused at 1A (500 mA nominal). Modular wall transformer available for 120 VAC nominal operation
Size and Weight	1.75"H X 19"W X 6.75"D (Rack-mountable) 3 lbs
Temperature Range	0 to +60 degrees C., 32 to +140 degrees F.
RADIO INTERFACE, FROM/TO TERMINAL or RECEIVER
Digital Data	Wide voltage input range: 200 mV to +/- 15 V. RS-232, CMOS, TTL or discriminator outputV
Inhibit Output	(Active when buffer becomes full) 2 form C relay: 1 A MAX at 28 volts (resistive load)
RADIO INTERFACE OUTPUT, TO/FROM TRANSMITTER
Data Output	CMOS or RS-232 levels (jumper selectable). Jumper selectable return to zero or open circuit when transmission is completed
PTT Output	2 form C relay: 1 A MAX at 28 volts (resistive load)
COR Input	Relay closure to ground or CMOS voltage levels. Optional 10K ohm pullup (jumper selectable). Jumper selectable polarity. Selectable 1/2 or 2 second delay
FRONT PANEL INDICATOR and CONTROLS
Power LED	Red power ON indicator
Receive LED	Green - Indicates receiving POCSAG data
Transmit LED	Green - Indicates that the unit is transmitting
Data LED	Green - Gives a visual indication of the quality of reception. ON if code word had no errors, OFF if errors were detected
Buffer 1/2 Full Buffer 1/4 Full	Red - Binary indication of the amount of memory used
Digital Threshold	This adjustment is used to compensate for +/- 5 volt DC offset of the input signal. Additional internal jumper extends to +/-15 volt signals
LOGICAL OPERATION
Buffer Size	256 Kilobytes = 17 minutes at 512 baud or 7.25 minutes at 1200 baud
Data Format	POCSAG transmissions at 512 or 1200 baud
Operating Mode	Simplex operation. Stores one or more complete transmissions then outputs the transmission as soon as the channel becomes available
Error Correction	Up to two bit errors in the received code word can be detected and corrected. Uncorrectable code words are replaced by idle codewords