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CHAPTER 2: Introduction

2.1.5 R

ECEIVER

The receiver contains several circuits (shown in Figure 2-1 below):

• The RECEIVE FILTER removes all the out-of-band frequencies.

• The AUTOMATIC EQUALIZER is made up of several equalizers activated

according to data rate.

• The digital AGC (automatic gain control) automatically compensates for

the attenuation of the line. You can choose between the two modes of AGC
operations by setting the AGC jumper:

ON: The AGC operates continuously.

CNTR: The AGC is active only when DCD is ON. When DCD is OFF,

the AGC will remain in the state to which it was most recently set.

In full-duplex point-to-point applications, there is no difference between the
two AGC modes of operation.

Figure 2-1. Block diagram for the LDM-MR19.2.

ENCODER
CONTROL

RTS
CTS

MODULATOR

TIMING

POWER
SUPPLY

RPF

GENERATOR

(STANDALONE

ONLY)

ENCODER

MODULATOR

RLB

COMMAND

GENERATOR

ASYNC TO

SYNC CONV

RLB

COMMAND

DECODER

RPF

DECODER

(CARD

ONLY)

CARRIER

DETECT

TIMING

RECOVERY

DECODER

AUTOMATIC

EQUALIZER

AGC

RCV

FILTER

EXT
CLK

TCX

REM
LOOP 2

TXD

SYNC

ASYNC

SELECTABLE

XMT AMPLIFIER

DIG LPBK

LOOP 3

ANA LOOP

RCV RLB

ANA LPBK

XMT

RCV

104 (BB) RXD

115 (BB) RXC

109 (CF) DCD

PIN 22

PIN 11

RPF LED

RPF RESET

DATA RATE

RV CLK

Summary of Contents for LDL-MR19.2

Page 1: ...y to midnight Friday 877 877 BBOX FREE technical support 24 hours a day 7 days a week Call 724 746 5500 or fax 724 746 0746 Mail order Black Box Corporation 1000 Park Drive Lawrence PA 15055 1018 Web site www blackbox com E mail info blackbox com JULY 2000 ME760A R2 ME760AE R2 ME760C 19 2 kbps RS 232 Line Driver LDM MR19 2 ...

Page 2: ... is operated in a commercial environment Operation of this equipment in a residential area is likely to cause interference in which case the user at his own expense will be required to take whatever measures may be necessary to correct the interference Changes or modifications not expressly approved by the party responsible for compliance could void the user s authority to operate the equipment Th...

Page 3: ...bo sótano mojado o cerca de una alberca etc 6 El aparato eléctrico debe ser usado únicamente con carritos o pedestales que sean recomendados por el fabricante 7 El parato eléctrico debe ser montado a la pared o al techo sólo como sea recomendado por el fabricante 8 Servicio El usuario no debe intentar dar servicio al equipo eléctrico más allá a lo descrito en las instrucciones de operación Todo ot...

Page 4: ...contactos y receptáculos donde salen del aparato 14 El equipo eléctrico debe ser limpiado únicamente de acuerdo a las recomendaciones del fabricante 15 En caso de existir una antena externa deberá ser localizada lejos de las lineas de energia 16 El cable de corriente deberá ser desconectado del cuando el equipo no sea usado por un largo periodo de tiempo 17 Cuidado debe ser tomado de tal manera qu...

Page 5: ...TRADEMARK USED IN THIS MANUAL AS 400 is a registered trademark of International Business Machines Corporation Any other trademarks mentioned in this manual are acknowlegded to be the property of the trademark owners ...

Page 6: ... 21 4 Card Installation 26 4 1 The RackNest 2 14 26 4 2 The RackNest 2 14 s Power Supply 27 4 3 The RackNest 2 14 Illustrated 28 4 4 Card Configuration Procedure 31 4 5 Card Installation Procedure 35 5 Operation 36 5 1 Controls and Indicators 36 5 2 Turning the Unit ON 39 5 3 Operating Procedure 39 5 4 Remote Power Failure RPF 39 5 5 Turning the Unit OFF 40 5 6 Reconfiguration 40 6 Troubleshooting...

Page 7: ...Either internal external from local DTE or recovered from remote LDM MR19 2 Data Format 5 6 7 or 8 data bits 1 1 5 or 2 stop bits even odd or no parity but see Table 3 3 on page 26 Operation 2 or 4 wire half duplex or 4 wire full duplex point to point or multipoint Data Rate Sync 1 2 2 4 3 6 4 8 7 2 9 6 14 4 or 19 2 Kbps Async Up to 19 2 Kbps RTS CTS Delay 0 8 or 64 ms user selectable Modulation D...

Page 8: ... 14 Jumpers Transmit timing 2 or 4 wire operation CTS delay Carrier control Transmit level Transmit line impedance Receive line impedance Enable disable analog loopback command on Pin 18 Enable disable remote loopback command on Pin 21 Enable disable front panel pushbuttons Connect disconnect signal ground and chassis ground AGC control Activate deactivate V 54 delay ME760A E R2 only Enable disabl...

Page 9: ...ME760A 115 VAC 47 to 63 Hz 3 watts input cord terminated with N American standard NEMA 5 15P plug ME760AE 230 VAC 47 to 63 Hz 3 watts input cord unterminated when shipped terminated by user Protection AC DC overvoltage protection circuits connected through transformers to transmit and receive lines Mean Time Between Failures 163 000 hours Temperature Tolerance 32 to 158 F 0 to 70 C Humidity Tolera...

Page 10: ... mi 7 5 km 14 400 15 2 mi 24 5 km 6 8 mi 11 km 5 1 mi 8 2 km 9 600 18 mi 29 km 8 mi 13 km 5 9 mi 9 5 km 7 200 20 5 mi 33 km 9 3 mi 15 km 6 9 mi 11 km 4 800 22 3 mi 36 km 9 9 mi 16 km 7 4 mi 12 km 3 600 24 8 mi 40 km 11 1 mi 18 km 8 3 mi 13 5 km 2 400 29 2 mi 47 km 13 mi 21 km 9 7 mi 15 7 km 1 200 34 1 mi 55 km 17 4 mi 28 km 13 mi 21 km ...

Page 11: ... AC or DC overvoltages The protection circuitry allows operation even when DC is connected to the line because of the following features Transmit Level and Transmit and Receive Impedances are independently selectable Transmit timing is provided internally derived externally from the data terminal or regenerated from the Receive signal Receive timing is regenerated from the Receive signal Line comm...

Page 12: ...e in one of five modes 4 wire full duplex 4 wire half duplex 2 wire half duplex 4 wire multipoint 2 wire multipoint 2 1 2 MODULATION TIMING The modulation timing circuit supplies the Transmit clock to the encoder Four clock sources are available INT CK internal clock from the modem s internal crystal oscillator EXT CK external clock from DTE Pin 24 RCV CK receive clock recovered from Receive signa...

Page 13: ...e remote converter adds a shorter stop bit before sending the data to the remote DTE For frequency deviations of up to 1 1 the stop bits should be shortened every eight characters 12 5 For frequency deviations of 1 2 to 2 3 the stop bits should be shortened every four characters 25 Use switch position 2 S2 of the ASYNC LENGTH DIP switch to select 25 or 12 5 frequency deviation For proper operation...

Page 14: ...DCD is ON When DCD is OFF the AGC will remain in the state to which it was most recently set In full duplex point to point applications there is no difference between the two AGC modes of operation Figure 2 1 Block diagram for the LDM MR19 2 ENCODER CONTROL RTS CTS MODULATOR TIMING POWER SUPPLY RPF GENERATOR STANDALONE ONLY ENCODER MODULATOR RLB COMMAND GENERATOR ASYNC TO SYNC CONV RLB COMMAND DEC...

Page 15: ...ms when the data rate is greater than or equal to 4 8 Kbps Table 2 1 below contains general guidelines for choosing AGC and CTS delay settings Each application is unique however you might find that your LDM MR19 2 system works better when the units are set slightly differently Table 2 1 Recommended Multipoint AGC and CTS Delay Settings Distance Data Rate Master Master Slave Slave Between AGC CTS D...

Page 16: ...end to a DDS network set the V 54 DELAY jumpers of the modems located close to the DDS network to ON to prevent multiple loopbacks The DELAY switch prevents the last modem from receiving the complete V 54 data sequence and being induced into a loop V 54 is required only for operation in synchronous mode NOTE The V 54 DELAY jumper must be set to OFF when you operate in asynchronous mode 2 2 Applica...

Page 17: ... LDM MR19 2 LDM MR19 2 LDM MR19 2 SLAVE 1 XMT IMP 150Ω RCV IMP HIGH SLAVE 2 XMT IMP 150Ω RCV IMP HIGH SLAVE 3 XMT IMP 150Ω RCV IMP HIGH SLAVE N XMT IMP 150Ω RCV IMP 150Ω A S 400 LDM MR19 2 LDM MR19 2 PC 4 wire twisted pair up to 34 mi 55 km AS 400 MASTER XMT IMP LOW RCV IMP 150Ω AS 400 PC running emulation software ...

Page 18: ...F LDM MR19 2 EXT CLOCK V 54 DLY ON LDM MR19 2 EXT CLOCK V 54 DLY ON LDM MR19 2 RCV CLOCK V 54 DLY OFF MASTER LDM MR19 2 SLAVE LDM MR19 2 SLAVE LDM MR19 2 SLAVE LDM MR19 2 CSU DSU CSU DSU PC running 5250 emulation software The XMT and RCV impedances of all the LDM MR19 2s in this application would be set to 150 ohms DIGITAL SERVICE NETWORK Cross pinned cable such as our EYN255C ...

Page 19: ...our unit is a 230 VAC ME760AE R2 model 3 2 Physical Placement Place the LDM MR19 2 on a tabletop or bench within 5 feet 1 5 m of a grounded 3 wire AC outlet and within 50 feet 15 2 m of the associated data terminal The unit is not designed to be bolted down Allow at least 36 inches 90 cm of clearance in front of the unit so you can operate and maintain it Be sure to leave 4 inches 10 cm of clearan...

Page 20: ...List CCITT EIA DTE SIGNAL V 24 RS 232 C PIN NAME DESCRIPTION 101 AA 1 Protective Chassis ground Can be isolated from Ground Signal Ground refer to GND Strap in Table 3 2 102 AB 7 Signal Ground Common signal DC power supply ground N A N A 9 8 volts Output 8 VDC 10 8 volts Output 8 VDC 103 BA 2 Transmitted Serial digital data received from sent by the Data local DTE See the Note on the next page 104...

Page 21: ...verns the Transmitted Data Timing signal See the Note below 115 DD 17 Receiver Signal Synchronous data rate clock output sent to Element Timing the local DTE Governs the Received Data signal See the Note below 142 25 Test Indicator The LDM MR19 2 sends a high positive level to the local DTE during any test mode 141 18 Loop 3 When it receives this control signal from the Test Command local DTE the ...

Page 22: ...ons in Figure 3 2 on page 27 CAUTION Be sure the LDM MR19 2 is unplugged before you open it To set internal jumpers and switches follow the steps below 1 Loosen the screw holding the top cover in place located at the top of the rear panel 2 Remove the top cover 3 Adjust the jumpers and switches for the configuration you want 4 Replace the top cover and tighten the retaining screw 3 5 AC Power Cord...

Page 23: ...LAY 8 ms 8 ms 64 ms No 5 Determines the transmit carrier mode ON ON CARRIER ON Transmit carrier is constantly ON CTRL CTRL Transmit carrier is ON only when RTS is high CTRL should be used in multipoint applications No 6 Determines transmit output level to the 0 dBm 0 dBm XMT LEVEL line 3 dBm 6 dBm 9 dBm No 7 Determines transmit line impedance 600 XMT IMPD For multipoint applications set the 300 ma...

Page 24: ...at last level of amplification if DCD goes OFF No 14 ON Activates V 54 delay preventing ON V 54 DLY multiple loopback of tail end circuits OFF OFF OFF No delay No 15 S3 and S4 determine character lengths S3 S4 bits ASYNC when unit is in async mode See OFF OFF 8 LENGTH Table 3 3 on the next page OFF ON 9 ON OFF 10 10 bits ON ON 11 S2 determines amount of stop bit ON 25 shortening for async mode OFF...

Page 25: ...tting Start Bit Data Bits Parity Stop Bit s Total Bits Always 1 5 NONE 2 8 ODD OR EVEN 1 or 1 5 8 2 9 6 NONE 1 or 1 5 8 2 9 ODD OR EVEN 1 or 1 5 9 2 10 7 NONE 1 or 1 5 9 2 10 ODD OR EVEN 1 or 1 5 10 2 11 8 NONE 1 or 1 5 10 2 11 ODD OR EVEN 1 or 1 5 11 ...

Page 26: ... DIS PIN 18 AN LP ENABL DIS RPF ON OFF XMT IMPD 600 300 150 LOW CHAS GND DIS CONN RCV IMPD 600 300 150 HIGH XMT LEVEL 0dbm 3dbm 6dbm 9dbm XMT TIMING INT CK EXT CK RCV CK ASYNC CTS DELAY 0 msec 8 msec 64msec AGC CNTRL ON 2 4 WIRE 2W 4W CARRIER CNTRL ON SWITCH DIS EN V54 DLY ON OFF ASY LENGTH DATA RATE REM ANA DIG LEDs GND 16 10 9 7 8 12 6 4 2 15 14 1 13 3 5 11 ...

Page 27: ...nd use its connectors instead 4 1 The RackNest 2 14 The RackNest 2 14 is a special 19 rack component designed to host a number of our short haul modems and line drivers As shown in Figures 4 1 on page 30 and 4 2 on page 31 it consists of a rack chassis with one or two power supplies into which you can plug as many as 14 modem or driver cards The Nest s rear panel consists of fourteen five screw te...

Page 28: ...essible AC outlet If your Nest is an RM110A you can use the power cord supplied with it if your Nest is an RM110AE use a power cord appropriate for your site s mains outlets The Nest begins operating and supplying power to the installed Cards as soon as it is plugged into a mains outlet and will continue operating until it is unplugged WARNING The RackNest 2 14 unit should always be grounded throu...

Page 29: ...LDM MR19 2 card in the RackNest 2 14 as shown in Figure 4 1 below The front and rear panels of the Nest are shown in Figure 4 2 on the next page the numbered connectors controls and indicators are described in Table 4 1 on page 32 Figure 4 1 The RackNest 2 14 Card installation ...

Page 30: ...29 CHAPTER 4 Card Installation Figure 4 2 The RackNest 2 14 illustrated GND RCV XMIT ON 1 7 2 5 3 4 6 ...

Page 31: ...ule Provides power to modules installed in the enclosure 3 ON Indicator Lights when power supply is operating 4 Chassis Ground Terminal Connector for attaching other grounds devices etc to the Nest s chassis ground optional 5 Power Connector Power connector with integral fuse 6 Main Channel Connectors J1 DB25 connectors for the module DTE connection 7 4 Wire Terminal Blocks TB1 For connection of 4...

Page 32: ...in Figure 4 1 on page 36 When you have everything at least tentatively decided identify the control s on the Card whose settings you want to change refer to Figure 4 1 then move the control s to your desired position s CAUTION Make sure the Card is disconnected from the RackNest 2 14 and from all sources of electric power WARNING HIGH VOLTAGE Any adjustment maintenance and repair of the Card under...

Page 33: ... 8 ms 8 ms 64 ms No 5 Determines the transmit carrier mode ON ON CARRIER ON Transmit carrier is constantly ON CTRL CTRL Transmit carrier is ON only when RTS is high CTRL should be used in multipoint applications No 6 Determines transmit output level to the 0 dBm 0 dBm XMT LEVEL line 3 dBm 6 dBm 9 dBm No 7 Determines transmit line impedance 600 XMT IMPD For multipoint applications set the 300 maste...

Page 34: ... DIS CONN DIS Isolates grounds from each other No 13 ON AGC always ON ON ON AGC CTRL AGC ON if DCD is ON remains CTRL at last level of amplification if DCD goes OFF No 14 ON Activates V 54 delay preventing ON V 54 DLY multiple loopback of tail end circuits OFF OFF OFF No delay No 15 S3 and S4 determine character lengths S3 S4 bits ASYNC when unit is in async mode See OFF OFF 8 LENGTH Table 3 3 on ...

Page 35: ...BL DIS XMT IMPD 600 300 150 LOW CHAS GND DIS CONN RCV IMPD 600 300 150 HIGH XMT LEVEL 0dbm 3dbm 6dbm 9dbm XMT TIMING INT CK EXT CK RCV CK ASYNC CTS DELAY 0 msec 8 msec 64msec AGC CNTRL ON 2 4 WIRE 2W 4W CARRIER CNTRL ON SWITCH DIS EN V54 DLY ON OFF ASY LENGTH DATA RATE REM ANA DIG LEDs 10 9 7 8 12 6 4 2 15 14 1 13 3 5 11 RPF ...

Page 36: ...E to the corresponding DB25 connector J1 on the back of the Nest For detailed information on the pinout of the DB25 connector see Table 3 1 on pages 21 and 22 5 If you haven t already done so install the remote RackNest 2 14 then repeat steps 1 through 4 at the remote site 6 Run twisted pair cable between the local and remote cards If you re running a 2 wire line Run one wire pair between the XMT ...

Page 37: ...ion before you attempt to operate it 5 1 Controls and Indicators All of the LDM MR19 2 s external controls and LED indicators are located on the unit s front panel as shown in Figure 5 1 below standalone or Figure 5 2 on the next page card The numbers and letters under the Item heading in Tables 5 1 and 5 2 on page 40 correspond to the numbers and letters in Figures 5 1 and 5 2 Figure 5 1 The stan...

Page 38: ...37 CHAPTER 5 Operation Figure 5 2 The LDM MR19 2 card s front panel PWR RTS TD RD DCD TEST RPF DIG ANA REM 1 2 3 4 5 7 A 6 B C D ...

Page 39: ...opback can also be activated from the terminal when the Pin 21 strap strap 10 is set to RLB EN see Section 3 4 D RPF ME760C only Turn OFF the RPF LED and reset the RPF circuitry see Section 5 4 Table 5 2 Indicators ITEM INDICATOR CCITT V 24 FUNCTION CIRCUIT 1 PWR Green LED is ON when power is present 2 RTS 105 Yellow LED is ON when DTE activates Request to Send 3 TD 103 Yellow LED is ON when stead...

Page 40: ...rocedure The LDM MR19 2 can operate entirely unattended However you should check the unit s LED indicators once in a while to make sure that everything is OK While the unit is ON operating personnel are not exposed to voltages in excess of 30 volts on its circuit board or on any accessible area of the unit s DC power supply Regardless of this do not open the unit while it is ON 5 4 Remote Power Fa...

Page 41: ... can take down the whole LDM MR19 2 network without pinpointing where the failure has occurred 5 5 Turning the Unit OFF To turn OFF the LDM MR19 2 unplug its AC power cord standalone units or turn OFF or unplug the RackNest 2 14 card units 5 6 Reconfiguration If at some point you need to reconfigure the LDM MR19 2 to operate differently with a new data rate or new clock source for example you can ...

Page 42: ...see Figure 6 1 on the next page Perform the test separately at the local and remote sites 1 Press the ANA Analog Loopback pushbutton on the front panel of the unit you want to test The TEST LED should light The LDM MR19 2 s transmit output is now connected to its own receiver 2 Verify that the data terminal equipment DTE is operating properly and can be used for testing If you find a fault call a ...

Page 43: ...s REM button causes a loopback at the remote LDM MR19 2 2 Perform a terminal test or BERT see Section 6 1 1 3 If Step 2 indicates a fault and if the modem test described in Section 6 1 1 was successful for both modems the telephone line circuits are not operating properly 6 1 2 B Local Digital Loopback To activate this test press the DIG pushbutton Pressing the local unit s DIG button causes it to...

Page 44: ...19 2 in digital loopback Figure 6 3 A local LDM MR19 2 in digital loopback RCVR DATA CLK DIG PRESSED LOCAL DATA TERMINAL RCVR XMTR DATA CLK REMOTE DATA TERMINAL XMTR LOCAL DATA TERMINAL XMTR RCVR DATA CLK CLK DATA RLB PRESSED REMOTE DATA TERMINAL RCVR XMTR ...

Page 45: ...ncluding the nature and duration of the problem when the problem occurs the components involved in the problem any particular application that when used appears to create the problem or make it worse the results of any testing you ve already done 6 3 Shipping and Packaging If you need to transport or ship your LDM MR19 2 Package it carefully We recommend that you use the original container If you ...

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