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MFJ-1270C/1274C MANUAL HARDWARE
Page 213
5 Transmit
Audio
External Modem Interface Connector - J14
Modem Disconnect Header- J4
The modem disconnect header, J4, on the MFJ-TNC PC board is provided for
using an external modem with the MFJ-TNC. This allows use of higher-speed
modems, such as 9600 baud, or more sophisticated, higher-performance modems
for OSCAR or other uses.
The following information is primarily for those who wish to interface external
modems to the MFJ-TNC. Familiarity with modem and serial data channel
terms is assumed.
The signals used at connector J4 are at standard TTL interface levels. A TTL
high, or 1, is greater than +2.4 volts but less than +5.25 volts. A TTL low, or 0,
is less than 0.8 volts but greater than -0.4 volts.
DO NOT connect an RS-232C
level modem directly to J4!
NOTE:
The modem disconnect is similar, but not identical to that used in TNC
1. Be very careful about interfacing an external modem using the same
cabling you may have prepared for use with TNC 1!
The connector pin-outs are as follows:
Pin 1
Carrier Detect Input
This pin tells the SIO radio port that a valid data carrier has been detected. It
should be pulled high when no carrier is detected and low when a carrier is
present. This line must be implemented unless the software release notes
indicate otherwise. It is normally jumpered to pin 2 when the on-board modem
is used.
Pin 2
Carrier Detect Output
This pin is an output from the the on-board modem and satisfies the
requirements outlined for pin 1 above. It is normally jumpered to pin 1 when the
on-board modem is used.
Pin 3
SIO Special Interrupt Input
This signal is routed to the radio port DCD input pin on SIO U21. This signal is
normally used during modem calibration. It may also be used for other
Содержание MFJ-1270C
Страница 9: ...MFJ 1270C 1274C MANUAL TABLE OF CONTENTS viii...
Страница 20: ...MFJ 1270C 1274C COMPUTER INTERFACING Page 11 20 Fig 2 3 Serial port wiring with jumpers for auxiliary signals...
Страница 241: ...MFJ 1270C 1274C MANUAL APPENDIX A RADIO HOOKUP Page 232...
Страница 258: ...MFJ 1270C 1274C MANUAL APPENDIX F JUMPERS Page 249 Fig G 1 Jumper Connector Location...
Страница 264: ...MFJ 1270C 1274C MANUAL INDEX Chapter 16 Page 29...