Midian TDM-1 User manual

COPYRIGHT2000 MIDIAN ELECTRONICS INC. ALL RIGHTS RESERVED.
Software Version 1.0 5-12-00
MIDIAN ELECTRONICS, INC. 2302 East 22nd Street Tucson, Arizona 85713
To Order: 1-800-MIDIAN'S Telephone: [phone] Fax: [phone]
TDM-1
TRANSPARENT OR ADDRESSABLE RADIO DATA MODEM
INSTRUCTION MANUAL
Features
• 1200 baud modem for point to point to multi-point
communications
• Simplex or full-duplex operation
• 63 character flow control buffer processor
• Automatic push-to-talk with front porch key-up delay
• Carrier/CTCSS busy detect input
• DB-25 connector houses the electronics
• RJ-11 connector cable picks up the following:
•battery
•ground
•push-to-talk
•mic audio
•receive audio
•Carrier/CTCSS busy from radio
• User to provide their own radio interface connector on
free end of RJ-11 cable
American Communication Systems
Discover the Power of Communications
™
TO ORDER –VISIT http://www.ameradio.com

PAGE 2
TDM-1 v 1.0 5-12-00
SPECIFICATIONS
VOLTAGE/CURRENT
Operating Voltage ......................................... 5.5-16 VDC
RX Mode Current................................................... 15 mA
TX Mode Current................................................... 20 mA
TX OUTPUTS
Output Baud Rate.................................... 1200 baud FSK
Tone Frequencies...... CCITT V.23, Freq. 1302 & 2097 Hz
PTT Output Current............................................. 100 mA
TX Audio Output Level .......................100 mV –1.3 V p.p.
Audio Output Impedance ................................. 3KΩ(min)
RX INPUTS
RX Audio Input Level..........adjustable, 200 mV p.p. (min)
RX Audio Input Impedance .............................50KΩ(min)
LEDs
RS232 In Data Indicator .........................................green
RS2332 Out Data Indicator..........................................red
TIMING
Front Porch Key-Up Delay ..................... 0.1-5.9 seconds
PTT Hang Time....................................... 0.1-5.9 seconds
COR Hold (Busy Lockout) Timer ............. 0.1-5.9 seconds
MECHANICAL
Standard DB25 connector
Operating Temperature ................................. -25°-70°C
WARRANTY
Midian Electronics, Inc., warrants this product to be
free from defects in material and workmanship for
two yearsfrom dateof shipment.Ifsuch
malfunction occurs, it will be repaired or replaced
(at our option) without charge for materials or labor
if returned to the factory. This warranty does not
apply to any parts damaged due to improper use--
including accident, neglect, unreasonable use, and
improper installation--or to unauthorized alterations
or modifications of the equipment. It does not
extend to damage incurred by natural causes such
as lightning, fire, floods, or other such catastrophes,
nor to damage caused by environmental extremes,
such as power surges and/or transients. It does not
extend to microprocessors, if it is determined by
Midian that the failure of a micro is due to static
damage, application of improper voltages to the
unit, or other problems not related to circuit design.
In such case or in the case of a desire to update the
micro to a different version of software, such
request must be specified in writing, and there will
be a charge agreed upon by both parties.
This product is warranted to meet published
specifications and to operate as specified only
when properly installed in radio equipment which
complies with U.S. FCC specifications and the
applicable radio manufacturer's specifications.
Midian Electronics is not responsible for any
operational problems caused by system design,
outside interference, or improper installation.
Equipment for repair can be returned to the factory
without prior written authorization. A brief letter
describing the nature of the defect should be
included with the merchandise. Repair by other
than Midian Electronics, Inc., will void this warranty.
In-warranty merchandise must be shipped, freight
prepaid, to Midian Electronics. Midian Electronics
will return, freight prepaid via UPS ground, the
repaired or replaced equipment to purchaser, within
the United States. Out-of-warranty repairs will be
billed at the rate of $60 per hour, plus replacement
parts.
This warranty applies to the original purchaser of
the equipment only. Midian Electronics is not liable
under this warranty, or any implied warranty, for
loss of use or for other consequential loss or
damage experienced by the purchaser. Some
states do not permit the exclusion or limitation of
implied warranties or consequential damages. This
warranty provides special legal rights, and the
purchaser may have other rights that vary from
statetostate.
Copyright Notice
The information in this manual and any software in
this product remain the property of MIDIAN
ELECTRONICS, INC. Reproduction, duplication, or
disclosure is not permitted without the prior written
consent of MIDIAN ELECTRONICS, INC.

PAGE 3M
IDIAN ELECTRONICS INCORPORATED
TDM-1 v 1.0 5-12-00
TABLE OF CONTENTS
SPECIFICATIONS ................................................................................................................................. 2
INSTALLATION INSTRUCTIONS .............................................................................................................. 4
1. OPERATION ........................................................................................................................... 5
1.1. GENERAL .......................................................................................................................................... 5
2. PROGRAMMABLE FEATURES ............................................................................................. 5
MENU SYSTEM ........................................................................................................................................ 5
2.1 PROGRAMMABLE FIELDS........................................................................................................... 5
A) KEYUP DELAY (0.4 SECONDS) ................................................................................................................ 5
B) PTT HANG TIME (1.5 SECONDS).............................................................................................................. 6
C) COR HOLD TIME (0.4 SECONDS)............................................................................................................. 6
D) COR POLARITY (1)................................................................................................................................ 6
E) PTT POLARITY (0) ................................................................................................................................. 6
F) BUSY LOCKOUT (0) ................................................................................................................................ 6
G) CONTINUOUS TONE (0).......................................................................................................................... 6
(H,I,J,K)A
DDRESSABILITY FEATURE ......................................................................................................... 6
3. TECHNICAL INFORMATION.................................................................................................. 7
3.1 RS-232 HANDSHAKING ............................................................................................................ 7
3.2 MODEM TO RADIO INTERFACE.................................................................................................... 7
3.3 TROUBLESHOOTING Q & A ....................................................................................................... 7
4. ACRONYMS............................................................................................................................ 8
SCHEMATIC
PICTORIAL

MIDIAN ELECTRONICS INCORPORATED PAGE 4
TDM-1 v 1.0 5-12-00
INSTALLATION INSTRUCTIONS
Installation Note:
Midian products utilize CMOS integrated circuits, which are susceptible to damage from high
static charges. Be sure to follow standard antistatic procedures when handling, including using grounded workstations
and soldering irons and wearing grounding bracelets.
Wire Function Instructions
RJ-11 Connector (radio)
Black Ground Connect to ground point in the radio. Can usually be connected to the mic jack.
Red 5.5 - 16 VDC Connect to switched B+ in radio. Can usually be connected to the mic jack.
White COR/COS (Carrier
Detect) In or
CTCSS Detect
Connect to point in Squelch or CTCSS circuit that changes logic level between 0 and 5 volts DC
when carrier is received. This is usually not available on the mic jack. A jumper can be connected
from the COR circuit to a spare pin on the mic jack. The COR wire is not mandatory. It prevents the
TDM-1 from producing garbage data on voice or squelch noise. The COR wire could be programmed
for positive polarity and then shorted to the PTT wire. When the unit is transmitting the COR will
see a busy and no data will be decoded. In full duplex operation the COR wire can be omitted. The
TDM-1 ships with the carrier detect input set for positive polarity (5V =carrier detected). If
necessary, re-program the COR polarity via the menu system.
Yellow RX Tone Data In Connect to a receive audio point in receiver, preferably to a point with a fixed audio level (before the
volume control). Can usually be connected to the mic jack but be careful to set volume control and
mark it. It will also be necessary to set the RX level pot R6 for proper level (0.5 to 2.0 Vpp at
pin 4 of IC-2). If using the radio’s volume control this pot could be set to perhaps mid-range and
then the radio’s volume control set to the optimal level and marked or somehow prevented from
being moved.
Blue TX Tone Data Out Connect to modulator circuit – usually at the mic jack. Using TX level pot R7 set the modulation
on wide band to be about 3-3.5 kHz of modulation. On narrow band systems set the modulation
from 1.5 to 1.8 kHz. Sending a data file during this time will key the transmitter and generate tone
data modulation.
Green PTT out Connect to the radio’s PTT circuit. TDM-1 now has control of PTT and will keythe radio whenever data is being
transmitted. Can usually beconnected to the mic jack.
DB25 Connector P2 (DTE)
P2-7 Ground Picks up computer or DTE ground.
P2-5 Clear to Send Applies Clear to Send (CTS) to the computer or DTE.
P2-3 RX Data Applies RX data to the computer or DTE.
P2-2 TX Data Picks up transmit data from the computer or DTE.
NOTE: Be sure to adjust the audio input and output level pots as described above. This will require opening the DB-
25 shell.
MODEM SETTINGS: Any device connected to the RS-2332 port of this modem must be configured for 1200 baud, 8
data bits, 1 stop bit, and no parity . Hardware flow control should be enabled if available. The modem is configured
as an RS-232 DCE device and therefore must be connected to a DTE device. See description of DTE at the end of
this manual for more information.
OPTIONAL SQUELCH OUTPUT: Pins 1 or 20 of IC-1 may be connected to customer supplied circuitry to squelch
the radio speaker while data is being received by the modem. Pin 20 goes high while data is being received, pin 1
goes low. Squelch outputs are activated as soon as a character is received by the modem. They are deactivated
when COR drops. Please note that voice or noise on the channel could be interpreted as data and cause the squelch
outputs to activate. Warning: These pins are unprotected microprocessor outputs. Customer supplied circuitry must
include current limiting and transistor buffering to protect the outputs. Failure to do say may damage the
microprocessor and void the warranty.
ERROR REDUCTION: Using the COR/COS/CTCSS lead can help minimize falsing on voice or noise. The TDM -1 will
receive data at a 12 dB SINAD point with numerous errors. Quieting the radio to about 17 dB will give little or no
errors. Most manufacturers will set the squelch point of their radios to about 12 dB SINAD. We recommend tightening
the squelch adjustment to 17 dB SINAD so that the radio will not unsquelch on a weak, noisy signal. Most radios have
a 12 dB SINAD point for about .25 µV of sensitivity. At 17 dB SINAD the receiver will have about .3 µV of sensitivity.
This should give virtually error-free data. Fully quieting the radio at or above .5 µV of sensitivity is recommended.

MIDIAN ELECTRONICS INCORPORATED PAGE 5
TDM-1 v 1.0 5-12-00
1. OPERATION
1.1. General
The TDM-1 is a 1200 baud FSK modem that employs the
CCITT V.23 signaling frequencies of 1302 and 2097 Hz. It is
capable of simplex, half, or full duplex operation.
The TDM-1 can serve as a transparent data modem or an
addressable transparent data modem. There are 4 registers
that can be programmed with a unique 4-character address ID
so that the modem will not pass any data sent to it without the
proper header ID.
The unit is available in a DB25 connector, which is designed
to plug into the back of a PC or any device with a standard
RS-232 serial port (also know as Data Terminal Equipment, or
DTE). In portable PC units it may be necessary to use a 9-pin
to 25-pin adapter between the PC and TDM-1 modem.
The radio side of the modem employs an RJ-11 connector
with a flying lead cable that can usually be connected to the
mic jack of most mobile radios. If possible it is best to utilize a
radio with a flat modulation response where the pre-emphasis
and de-emphasis can be turned off.
The TDM-1 employs a modem chip, an RS232 converter chip,
and a microprocessor buffer to control flow between them.
Most simple modems have no flow control or data buffer.
They simply apply a request to send line to key the radio’s
PTT and instantly begin sending data. The TDM-1 buffers
approximately 500 milliseconds of data (up to 63 characters).
This gives the radio time to key-up and for CTCSS to open
the receiving unit’s decoder or repeater before sending the
data. Upon receipt of the 61st character from the DTE, the
TDM-1 will drop the CTS (Clear to Send) line to the DTE,
halting further data. This is known as hardware flow control. If
the programmed key-up delay exceeds 500 milliseconds,
hardware flow control must be enabled in the DTE or data
may be lost.
2. PROGRAMMABLE FEATURES
MENU SYSTEM
The following describes the TDM-1 menu system used for
setting the modem parameters. In order to use the menu
system, the modem must be connected some sort of terminal.
A personal computer running a dumb terminal program is
typically used. See topic Terminal Software in the
Troubleshooting section of this manual.
To enter the menu system, stop transmitting data. Type ###
quickly, (within about 1 second). The menu appears after a
short delay, provided no other characters are typed. The
menu will appear as follows. The values shown are the factory
defaults.
There are 3 types of fields, binary fields, 2 digit
fields and 4 character fields. Binary fields are either
‘0’ or ‘1’. A ‘0’ means a feature is OFF or a polarity
is NEGATIVE (active LOW). A ‘1’ means a feature
is ON or a polarity is POSITIVE (active HIGH).
A 2-digit field is for timers such as key-up delay. All
timers can be set for 0.1 to 5.9 seconds. Four
character fields are for addresses (see below). To
change a particular item, simply press the letter key
corresponding to the item to be changed. If for
example, B is pressed, the following will be
displayed:
PTT Hang Time 1.5s >
If you do not wish to change the setting, press
ENTER. Otherwise, type both digits of the new hang
time. The decimal point will be placed automati-
cally. There is no need to press the ENTER key.
The entire menu will automatically be re-displayed
reflecting the changed parameter. Only legal
characters will be accepted, others will be ignored
until 2 legal characters are typed (or ENTER is
pressed). Binary and address fields operate in a
similar manner. Parameter changes are
automatically saved to EEPROM as they are typed.
When all changes are complete, select option
L
to
return the modem to normal operation.
2.1 PROGRAMMABLE FIELDS
A) Keyup Delay (0.4 seconds)
The amount of time from when data is received
from the DTE to the time data begins being sent out
by the modem to the radio. PTT is asserted and
data carrier tone (1302 Hz) is turned on immediately
upon receiving the start bit of the first character.
The key-up delay is programmable from 0.1 to 5.9
seconds, which allows for a front porch key-up delay
Midian TDM-1 V1.0
A) Keyup delay 0.4s
B) PTT Hang Time 1.5s
C) COR Hold Time 0.4s
D) COR Polarity 1
E) PTT Polarity 0
F) Busy Lockout 0
G) Cont. Tone 0
H) Address #1 ----
I) Address #2 ----
J) Address #3 ----
K) Address #4 ----
L) Exit menu
Select >

MIDIAN ELECTRONICS INCORPORATED PAGE 6
TDM-1 v 1.0 5-12-00
time to open a repeater or mobile radio’s CTCSS decoder
before the data is transmitted. To compute the front porch
key-up delay time, EIA specs state that a CTCSS decoder
should open in 250 msec at 100 Hz. The time increases as
CTCSS frequencies decrease. Therefore, from the high-end
frequencies to the low frequency, the time could run 100 to
500 msec. In addition, transmitter synthesizer lock time can
also be a consideration and can vary from a few milliseconds
to 100 msec. Also, E & M lead on microwave systems that
can be tied to the repeater can add 50 to 100 msec delay.
Satellite voting systems can also introduce additional delays.
B) PTT Hang Time (1.5 seconds)
PTT remains asserted for this amount of time after the key-up
delay if no more data is being sent by the DTE. If additional
data is sent by the DTE, PTT will remain asserted for this
amount of time after the DTE stops sending data. This
minimizes keying and unkeying for slow typists. This time may
be reduced if data is being sent by automatic means. If the
key-up delay is 500 ms or less, program this time to be
greater than the key-up Delay. This will ensure that enough
time is available to transmit characters that were buffered
during the key-up Delay. If the key-up delay is 600 ms or
more, program this time for at least 600 ms.
C) COR Hold Time (0.4 seconds)
This applies to busy lockout only. The unit will not assert PTT
(if busy lockout is enabled) for this amount of time after carrier
drops. If the data buffer fills up during this time, the CTS line
will be dropped to prevent the DTE from sending more data.
Once this time and the front porch key-up delay time have
expired, the buffered data will be sent. CTS will once again be
asserted to allow data to flow.
If data is being sent over a channel employing voice, this
register should probably be programmed for 2 to 3 seconds to
prevent the TDM-1 from transmitting between short pauses in
someone’s conversation.
Note that this parameter is ignored if busy lockout is not
enabled in programmable field
F.
D) COR Polarity (1)
COR is internally pulled up and the default polarity is positive.
COR is used to qualify characters coming into the modem
from the radio receiver. If COR is not in the active state, data
will not pass from the modem to the RS-232 port.
COR is also used for the busy lockout function (see above).
If using full duplex mode it may not be necessary to connect
the COR wire provided it is programmed for positive polarity.
E) PTT Polarity (0)
Normally, the open collector PTT output is pulled to
ground to assert PTT. Almost all radios use a PTT
switch to ground. If using a radio with positive PTT it
may be necessary to add a pull-up resistor to the
open collector transistor on the TDM-1. If there is a
pull-up resistor in the radio this will not be
necessary. The pull-up resistor should be pulled up
to 5V logic when connecting to a microprocessor
PTT input. Anything higher than 5V could damage
the radio’s microprocessor.
F) Busy Lockout (0)
Enables busy lockout feature described under COR
Hold Time (field
C
).
Government regulations require radio users to open
tone squelch and monitor a channel before
transmitting. If they do not, they can interfere with
other users already on the channel. Busy Channel
Lockout automatically checks the channel, and will
not allow the transmitter to key-up and send data
until the COR Hold Time programmed in field
C
has
expired.
G) Continuous Tone (0)
By default, the modem will generate a data carrier
tone only during PTT. If full duplex or wire-to-wire
operation is desired, the carrier tone may be
enabled continuously by setting this field to a 1.
(H, I, J, K) Addressability Feature
Normally, all data received from the modem is
passed to the RS-232 port. If the addressability
feature is enabled, the modem will not pass data to
the RS-232 port until one of the four, 4-character
decode addresses appears in the data stream.
By default, the addressability feature is disabled. If
any of the address fields have a non-dash character
as the first character, the addressability feature will
be enabled. Any four printable characters may be
used as a decode address. There are a total of four,
4-character decode addresses available (H-K).
If, for example, address field H is programmed to
*123, the modem will not pass data until the
address string *123 appears in the incoming data
stream. All data following the *123 will be passed
from the modem to the RS-232 port. Data will
continue to pass until COR drops. The decode
system will be reset immediately after COR drops
and will have to be addressed again in order to pass
data. For this reason, COR must be connected in
order to use the adressability feature.

MIDIAN ELECTRONICS INCORPORATED PAGE 7
TDM-1 v 1.0 5-12-00
To disable the addressability feature, make certain the first
character of all four decode addresses is a dash (-) character
(the characters following the dash are ignored).
3. TECHNICAL INFORMATION
3.1 RS-232 HANDSHAKING
The CTS line is used by the modem during key-up delay to
prevent the DTE it is connected to from sending more
characters. The modem will buffer up to 63 characters during
the key-up delay, which allows for 500 ms of key-up delay
even if the CTS signal is ignored by the device connected to
the RS-232 port.
If the CTS signal is ignored or not connected, and the key-up
delay exceeds 500 ms, data will be lost:Each new character
after the 63rd will cause the oldest character in the buffer to be
discarded.
Normally, the CTS signal will be dropped as soon as the 61st
character is received, with the expectation being that the
connected device will buffer characters itself until CTS is once
again asserted (after front porch key-up delay period is
complete).
There is no buffering or handshaking in the opposite direction.
The DTE must be able to accept data coming in from the
modem at the same rate as the data is being received off the
air.
3.2 MODEM TO RADIO INTERFACE
As soon as data is received from the DTE, PTT to the radio
will be asserted (except when busy lockout is active). The
modem carrier tone is also turned on. Actual data
transmission on the TX out wire begins after the front porch
key-up delay.
Audio recieved from the radio is fed to the RX in wire and
translated to data and sent to the DTE’s RS-232 port. In order
to prevent noise on the air being translated as garbage
characters, COR is used. If COR is not active the modem
ignores incoming noise, voice, or data. If no COR wire is
used, data will pass all of the time since COR is pulled high
and programmed for positive polarity (by default). In this
configuration, the COR wire may be tied to PTT (of negative
polarity) to enforce simplex operation. This will also keep
noise or voice on the RX path from being interpreted as
garbage data while transmitting.
3.3 TROUBLESHOOTING Q&A
Is there any way I can test my TDM-1 to be sure it is okay?
Yes, you can perform a loop-back self-test. The TDM-1, as
shipped from the factory, may be self-tested using a dumb
terminal or dumb terminal program. Configure the terminal
settings for 1200 baud, 8data bits, 1 stop bit, and no
parity. Also configure the terminal for FULL
DUPLEX operation. Connect the blue and yellow
wires of the TDM-1 together, connect the TDM-1 to
the computer (or terminal), and apply power to the
TDM-1. Characters typed at the terminal should be
echoed back to the terminal by the modem. Note
that there will be a 0.4 second delay from the time
the 1st character is typed, to the time it is echoed
back. This is due to the default front porch key-up
delay of 0.4 seconds.
What is a ‘dumb terminal program’?
A real ‘dumb terminal’ is a device passes data from
its keyboard to its RS-232 (serial) port. It also
displays data coming into it from its RS-232 port,
usually to a CRT monitor. A ‘dumb terminal
program‘ is a software package that simulates the
operation of a dumb terminal on a personal
computer. Examples of dumb terminal programs are
PROCOMM (a popular shareware program), and
HYPER-TERMINAL, a program that is provided with
the Windows 95 and 98operating systems. Using a
dumb terminal is typicaly the most convenient way
to configure the TDM-1 parameters before placing
the product into service.
Please note: Midian does not make or sell dumb
terminal software for use with the TDM-1. Many
such programs are available at low or no cost such
as PROCOMM or HYPERTERMINAL. For
assistance in using such programs, or any device
connected to the TDM-1, please contact the
manufacturer of that program or device. A wealth of
information on this topic is also available on the
Internet.
Why can’t I see anything I am typing using a
dumb terminal program?
Your dumb terminal is set for FULL DUPLEX
operation. It is relying on the remote device to ‘echo’
what you type back to screen. A terminal set for
HALF DUPLEX will echo the characters itself.
Please refer to the instructions for your dumb
terminal for more information.
I am using the TDM-1 menu system with my
dumb terminal, why does everything I type
appear twice?
The TDM-1 menu system automatically echoes
everything you type back to you for positive
confirmation. If you operate your terminal in HALF
DUPLEX mode, it too will echo the characters you
type. Place the terminal in FULL DUPLEX mode
while configuring your TDM-1 to avoid this nuisance.
Please refer to the instructions for your dumb
terminal for more information.
Why does everything I type appear on the same
line after I hit the ENTER key?
The ENTER key actually sends what is known as a
Carriage Return (CR) character. The CR character

MIDIAN ELECTRONICS INCORPORATED PAGE 8
TDM-1 v 1.0 5-12-00
places the cursor at the beginning of the line. To move to the
next line, a Line Feed (LF) character must be sent with the CR
character to go to a new line. Most terminal programs can do
this for you. Please refer to the instructions for your dumb
terminal for more information.
I am using the TDM-1 menu system with my dumb
terminal and a blank line appears after each line of the
menu and now I cannot see all of the options. What is
causing this?
The TDM-1 automatically places a carriage return and a line
feed (see above) at the end of each line so that the menu
options will not type over themselves on the same line. Your
terminal is itself adding a line feed for each carriage return
character it receives. This is typically a configurable option on
a dumb terminal. Please refer to the instructions for your
dumb terminal for more information.
Can I transfer data files between computers with the
TDM-1?
Yes, the TDM-1 will support straight ASCII or binary file
transfers (uploads and downloads). The TDM-1 will generally
not support file transfer protocols such as XMODEM,
YMODEM, KERMIT, etc. This is because the TDM-1 was
designed to accommodate 2-way radios and thus incorporates
PTT key-up delay, hang time, etc. These delays interfere with
the normal handshake of these full-duplex protocols.
Why are there errors in the data?
There are many possible causes for errors in data transmitted
over the air. These can range from a weak signal to outright
interference. The V.23 protocol does not implement any error
detection or correction. If you are seeing frequent data errors
and have a strong signal, you may need to adjust the TX and
RX level pots. You will need to open the DB-25 shell to make
these adjustments. See the installation page for details.
Why are there extraneous characters at the end of each
transmission?
The squelch tail heard on some radios at the end of a
transmission is often the cause of extraneous data. Try using
PL/DPL reverse burst on your radio to eliminate squelch tail.
Other possibilities include ANI signaling, voice talk-off, etc.
I connected my TDM-1 to a terminal and all I see is the
word TEST printing over and over again? What do I do?
The TDM-1 performs an EEPROM checksum test upon
power-up. This is done to verify the integrity of the
programmed parameters stored in EEPROM. Should this test
fail, the unit will repeatedly send the message TEST to the
DTE. To cancel the test mode and restore factory defaults,
send data from the DTE to the modem while the TEST
message is printing (eg. press any key). If this does not
restore operation, contact Midian for diagnostic proc edures.
4. ACRONYMS
This section is provided to clarify certain acronyms used in
this manual.
COR
This old radio term stands for Carrier Operated
Relay. For the purpose of this manual, this refers to
any signal which changes state when a radio detects
an RF carrier. Also known as Carrier Operated
Switch (COS).
CTS
Clear to Send. An RS-232 signal from a DCE to a
DTE used to control the flow of data from the DTE
(see definition of DTE below).
DCE
Data Communications Equipment (see DTE).
DTE
Data Terminal Equipment. For the purpose of this
manual, this is any device connected to the RS-232
port of the TDM-1. The TDM-1 can connect to any
device with an RS-232 port configured as a DTE.
This includes PC’s, laptop computers, handheld
terminals, dumb terminals, data terminals, GPS
modules, etc.
Historically, DTE refers to a dumb computer
terminal with an RS-232 port that can be connected
to a modem. A modem such as the TDM-1 is
considered to be Data Communications Equipment
(DCE).
Sometimes bar-code scanners and GPS modules
are configured as a DCE. If it is desired to connect
this modem to a device configured as a DCE, a null
modem will be required.
EEPROM
Electrically Erasable Programmable Read Only
Memory. This is a type of computer memory.
EEPROM retains the data stored in it for many
years, even if power is not applied. The TDM-1
employs EEPROM to store the user programmable
parameters such as Key-up delay. The EEPROM
may be re-programmed several thousand times.
TYPICAL NULL MODEM CONFIGURATION
DB25 PIN PIN
DB25
2 TX ------------------ RX 3
3 RX ------------------ TX 2
5 CTS ------------------ RTS 4
4 RTS ------------------ CTS 5
6 DSR ----------------+- CD 8
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