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Barnett Engineering B1474 - page 1
RA DIO MO DEM B1474 OP ER A TION MAN UAL April, 1998 Manual Revision 4.1 (for Version 2.1 Hardware) ...
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Barnett Engineering B1474 - page 2
TA BLE OF CON TENTS FCC RE QUIRE MENTS ................... 2 1 IN TRO DUC TION ...................... 3 2 SPEC I FI CA TIONS ..................... 5 3 NO TA TION ........................ 7 4 OP ER A TION ........................ 8 5 SETUP PRO CE DURES ................... 12 6 IN DI CA TORS ....................... 16 7 CON FIG U RA TION ............ ...
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Barnett Engineering B1474 - page 3
FCC RE QUIRE MENTS This equipment generates, uses, and can radiate radio frequency energy and, if not used in accordance with the instruction manual, may cause interference to radio communications. It has been tested and found to comply with the limits for a Class A computer device pursuant to sub-part J of Part 15 of FCC Rules, which are designed ...
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Barnett Engineering B1474 - page 4
1 IN TRO DUC TION The B1474 Radio Modem provides a reliable method of sending 1200 baud data signals over radio or cable facilities. Digital information is converted to tone format for transmission over the communication channel. Received tones are converted back to RS232 digital format. Hardware handshaking using RTS and CTS signals allows the rad ...
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Barnett Engineering B1474 - page 5
In di ca tors Modem status condition is indicated by front panel LEDs. The LEDs may be disabled to conserve power. B1474 BARNETT EN GI NEERING LTD. PAGE 4 ...
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Barnett Engineering B1474 - page 6
2 SPEC I FI CA TIONS GEN ERAL Trans mis sion Rate: 1200 Baud (Bell 202 sig naling) or V.23 if fac tory in stalled Trans mis sion For mat: 8 data bits, no par ity, 1 stop bit if mo dem buff er ing is se lected; oth er wise trans par ent Power Re quire ment: Op er ates from 12 to 30 VDC . Cur rent drain is 110 mA with the LEDs on, 65 mA with the LEDs ...
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Barnett Engineering B1474 - page 7
PTT Drop De lay: 0, 10, 20, 50, 75, 100 or 250 msec. Keeps trans mit ter keyed long enough to en sure squelch tail noise does n’t in ter fere with data at the re ceiv ing ter mi nal. Hand shak ing: Spec ifies the type of flow con trol used. 2/4 Wire: Se lects 2 or 4 wire ca ble op er a tion. LED Con trol: Dis ables LEDs to save power. Equal iza t ...
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Barnett Engineering B1474 - page 8
3 NO TA TION Throughout this manual, abbreviations will be used. These abbreviations are explained here for clarity. CD Carrier Detect COS Carrier Operated Switch CTS Clear To Send DCE Data Communications Equipment DTE Data Terminal Equipment FCC Federal Communication Commission GND Ground PTT Push To Talk RFCTS RF Clear To Send (used in trunking s ...
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Barnett Engineering B1474 - page 9
4 OP ER A TION The B1474 operates from 12 to 30 VDC to provide an interface between two computer devices and the communications channel. In the descriptions below it is assumed that the sending device uses a DCE configuration. Four different types of operation may be configured: Hard ware Hand shak ing Basic operation and timing using hardware hand ...
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Barnett Engineering B1474 - page 10
B1474 BARNETT EN GI NEERING LTD. PAGE 9 FIGURE 1 MODEM TIMING USING RTS AND CTS ...
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Barnett Engineering B1474 - page 11
Soft ware Hand shak ing Using XON / XOFF Basic operation and timing using XON / XOFF software handshaking are as follows: • The send ing com puter be gins send ing data. The for mat must be 8 data bits, no par ity, 1 stop bit. • Upon de tect ing data, the send ing mo dem per forms the fol low ing: – checks the chan nel, if this fea ture is en ...
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Barnett Engineering B1474 - page 12
– checks the chan nel, if this fea ture is en abled. If the chan nel is free, it as serts its PTT to power up the ra dio’s trans mit ter. If the chan nel is busy, it buff ers the re ceived data un ti l the chan nel be comes free. – pres ents MARK tone (car rier) onto the chan nel. – sets its RTS/ CTS de lay timer (from 20 to 300 msec). RTS/ ...
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Barnett Engineering B1474 - page 13
5 SETUP PRO CE DURES The semiconductors can be damaged by static discharge. Proper handling procedures must be followed . Do not touch any of the devices inside the modem, and work only in a static free, clean, and dry environment. (1) Re move The Top Cover Remove the two center screws on the top cover of the modem to release it from the base. Pull ...
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Barnett Engineering B1474 - page 14
GND (Chassis) Pin 1 TXD Pin 2 RXD Pin 3 RTS Pin 4 (connect only if using hardware handshaking) CTS Pin 5 (connect only if using hardware handshaking) GND (Signal) Pin 7 CD Pin 8 The cable and housing on the DB-25S socket must be shielded to conform to FCC, part 15-J/A standard s for emissions. Using a non-shielded cable may result in undesirable ra ...
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Barnett Engineering B1474 - page 15
Adjust R12 so that the modem waits when the channel is busy, and transmits when the channel is free. When the BUSY light is ON, the modem is waiting for the channel. To disable this feature, leave P1-9 unconnected and SW1.9 OFF. If Option 002 trunking software is used, set SW1.9 according to the polarity of the RFCTS signal connected into P1-9. Set ...
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Barnett Engineering B1474 - page 16
To operate full duplex, leave SW2.8 OFF. To operate half duplex, set switch SW2.8 ON. If a 2 wire circuit is used, the modem will only operate half duplex. RTS Con trol SW3.1, when ON, will assert RTS continuously. This causes PTT to be asserted and transmit tones to be generated. The switch should be on for a no handshaking, non-buffered configura ...
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Barnett Engineering B1474 - page 17
6 IN DI CA TORS The LED indicators on the front case are used to indicate modem status: RUN Power is on the modem. BUSY The modem is waiting to transmit but is held back by the squelch detector. RTS Request To Send from the computer is present or characters have been re ceived into the buffer. CTS Clear To Send is active. CD Carrier is detected on ...
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Barnett Engineering B1474 - page 18
B1474 BARNETT EN GI NEERING LTD. PAGE 17 7 CONFIGURATION RTS/ CTS DE LAY 20 X 50 3 msec 2 35 X 4 LEDS OFF X LEDS ON 1 LED CON TROL SWITCH 1 PTT DROP DE LAY 200 X 300 X X X 500 X X 1000 X X X 100 X X X X PTT RE GARD LESS OF RFCTS X PTT ON LY WITH RFCTS 10 SEND/RE CEIVE ( TRUNKING ON LY) NO XON / XOFF X USE XON / XOFF 8 XON / XOFF LOW = CHAN NEL FREE ...
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Barnett Engineering B1474 - page 19
B1474 BARNETT EN GI NEERING LTD. PAGE 18 BUFFER USE RTS/ CTS CON TROL X USE BUFFER 2 SWITCH 3 RTS ON 4 WIRE CA BLE X 2 WIRE CA BLE 4 RTS ON EX TER NAL RTS X RTS ON AT ALL TIMES 1 X 3 ...
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Barnett Engineering B1474 - page 20
B1474 BARNETT EN GI NEERING LTD. PAGE 19 +V 8 INPUT VO LT AGE GROUND TX WL TX WL TX RADIO 7 6 5 4 3 9 1 PIN SYMBOL DESCRIPTION GND 2 RX RADIO RX WL RX WL SQL PTT TRANSMIT OUTPU T , SINGLE ENDED TRANSMIT OUTPU T , BALANCED RECEIVE INPU T , BALANCED SQUELCH DETECTOR INPUT RECEIVE INPU T , SINGLE ENDED } } P3 DIG I TAL P1 AU DIO 8 PIN 7 5 4 3 2 1 10 S ...
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Barnett Engineering B1474 - page 21
9 BOARD L AY OUT B1474 BARNETT EN GI NEERING LTD. PAGE 20 ...
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Barnett Engineering B1474 - page 22
Barnett En gi neering Prod uct War ranty WARRANTY STATEMENT Barnett Engineering Ltd . warrants that all equipment supplied shall be free from defects in material or workmanship at the time of delivery. Such warranty shall extend from the time of delivery for a period of one year. Buyer must provide written notice to Barnett Engineering Ltd . within ...
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Barnett Engineering B1474 - page 23
11 AP PEN DIX A - OP ER A TION WITH A GE MARC V TRUNKING SYS TEM When ordered with the Option 002 trunking software, the B1474 will handle the special timing and control requirements of a GE Marc V trunking system. The following sections describe the connections to a trunking radio, and the slightly different operation of the radio modem. CON NEC T ...
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Barnett Engineering B1474 - page 24
B1474 BARNETT EN GI NEERING LTD. PAGE 23 FIGURE 2 MODEM TIMING FOR A GE MARC V TRUNKING SYSTEM USING RTS/ CTS HANDSHAKING ...
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Barnett Engineering B1474 - page 25
Soft ware Hand shak ing Using XON / XOFF Basic operation and timing using XON / XOFF software handshaking in a trunking system is as follows: • The send ing com puter be gins send ing data. The for mat must be 8 data bits, no par ity, 1 stop bit. • Upon de tect ing data, the send ing mo dem per forms the fol low ing: – checks the chan nel. If ...
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Barnett Engineering B1474 - page 26
No Hand shak ing Basic operation and timing with data buffering (no handshaking) in a trunking system is as follows: • The send ing com puter be gins send ing data. Data for mat must be 8 bits, no par ity, 1 stop bit. • Upon re ceiv ing data, the mo dem per forms the fol low ing: – checks the chan nel for RFCTS - if the chan nel has been as s ...
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