Tigertronics RTX-12 User manual

Model RTX-12 Radio Modem

154 Hillview Drive Grants Pass, Oregon 97527 (541) 474-6700 Fax: (541) 474-6703

- INTRODUCTION -

The RTX-12A and RTX12OEM are half-duplex 1200 baud

radio modems, designed especially for telemetry and remote

data transfer applications using inexpensive “voice grade”

radios. While the standard RTX modem is Bell 202

compatible, an optional CCITT v.23 model is available.

The RTX modems provides an inexpensive solution to

interfacing computers and microcontrollers to radio links.

The modem utilizes FSK audio tones to provide reliable

communications over narrow bandwidth channels. The

modem is easily interfaced to radios designed for either

telemetry or voice communications (hand-held, mobile or

base). The data interface is designed to be compatible with

both standard RS-232 levels and CMOS logic levels. The

total power consumption is less than 25 milliwatts, making

it ideal for battery powered applications. When operated

from a standard RS-232 port, no external power source is

required. The modem has it’s own micropower voltage

regulator, allowing it to operate from a single polarity

unregulated power source as low as +4.8 volts. Thus, it can

be powered directly from the +5 volt logic supply in

microcontroller applications.

The RTX-12 is available in two different versions: The

RTX-12A and the RTX-12OEM. Both versions are

functionally and electrically identical. The only difference

between them is their physical layout and the connectors

used for the radio and data interfaces. The RTX-12A is

packaged in a custom injection molded case and is designed

to plug directly into a standard 25-pin RS-232 serial port.

Connection to the radio is through an RJ-11 connector

(cable included). The RTX-12OEM model is intended for

embedded applications and is provided without an

enclosure. This modem is extremely small (1-1/4”x 1-

1/2”) and is easily installed inside other equipment. A

single 10-pin header provides connections for both the radio

and controller. An optional color coded ribbon cable is

available for this modem.

Both the RTX-12A and the RTX-12OEM are normally

supplied with full transmit and receive capability. However,

in high volume applications, either modem can be specially

ordered in a Transmit or Receive Only version.

- RADIO INTERFACE -

The radio interface on the RTX-12 consists of four signal

lines and is described in detail below. Please refer to the

“Specifications”section for the specific connector and pin-

out used with each version of the modem.

Ground - This is the signal ground for both microphone and

receive audio from the radio. It is also connected to power

ground in the modem.

PTT - This line is used to “key”the transmitter. The

modem switches this line to ground with a FET transistor,

when it receives a transmit command. The transistor can

“sink”currents as high as 50ma. When interfacing older

radios that use mechanical switches (relays) in the PTT

circuit, precautions must be taken to insure that voltage and

current limits are not exceeded (see specifications). Special

provisions have been made to key the PTT of some “hand-

held”radios. See the “HT Operation”section for details.

Rx Audio - This is the receive audio input to the modem. It

is high impedance and capacitively coupled inside the

modem. The nominal input level is 300mv p-p. A factory

option is available to attenuate this input and/or provide a

lower impedance if required. Care should be taken not to

overdrive this input (see specifications).

Mic Audio - This is the transmit audio output from the

modem. The output is capacitively coupled and should be

connected to the microphone input of the radio. The level

of this output can be adjusted by the “LEVEL”control on

the RTX-12 from zero to 290mv p-p (Hi Z). The output is

factory adjusted to 20mv p-p into a 1000 ohm load. This

level should be correct for most modern radios that use

“electret”type microphone inputs. A factory option is

available to modify the output level.

CAUTION - Be sure that the cable you plug into the RJ-11

connector (RTX-12A only) does not have the wires in

reverse order! Verify the orientation as follows: When

viewing the connector from the rear of the RTX-12A,

oriented such that the release lever is UP, the left most wire

MUST BE YELLOW.

Grants Pass, Oregon

- DATA INTERFACE -

The data interface on the RTX-12 consists of the six signal

lines described below. Please refer to the “Specifications”

section for the specific connector and pin-out used with

each version of the modem.

Transmit Data - Data from computer/microcontroller to the

modem. This input will accommodate either standard RS-

232 levels (+/- 12v) or CMOS logic levels (0/+5v). This

input is high impedance (see specifications).

Receive Data - Data output from modem to

computer/controller. Output levels are RS-232 compatible

or CMOS logic depending on the state of the Negative In /

PTT line (see below).

Negative In / PTT - This input determines the “low”voltage

level available from the “Receive Data”pin during receive

operation of the modem. For RS-232 applications, this

input should be set to a “low”level (-12v) by the software,

during receive. In logic level applications (CMOS), it

should be held at a low level (0v) during receive. This

input is also used to signal a transmit command to the

modem (PTT). Raising this input to a “high”level

(+12v/RS-232 or +5v/CMOS) will cause the modem to

enter transmit mode. In this condition, the PTT keying

transistor will be turned on and the FSK modulation will be

active on the microphone input of the radio.

Carrier Detect - This output from the modem indicates the

presence of valid carrier (tones) from the receiver. This

output can be monitored by the software to determine when

valid data is available. This output is “low”when carrier

tones are detected and “high”state when carrier is not

present.

Ground - This pin provides both signal and power grounds

to the modem.

Positive Supply - This input provides operating power to the

modem. In RS-232 applications, this pin should be held in

a “high”state (+12v) by the software at all times. In logic

level applications, connect this pin to any convenient source

of positive voltage (see specifications). Direct connection to

a +5 volt logic supply is satisfactory. The power supplied to

this pin is regulated within the modem, so an unregulated

source of power may be used (battery).

- HT OPERATION -

If you are connecting the RTX-12 to a hand-held radio, you

may find that there is no separate PTT input line. Many of

these radios key the PTT by grounding the microphone

input line through a resistor. If this is the case in your

installation, you can activate an internal PTT keying

resistor (2.7K) by installing a shunt across the “HT”jumper

on the modem. This jumper is located on the rear of the

RTX-12A, and just to the side of the 10-pin header on the

RTX-12OEM. If you use the keying resistor option, you

should not attach anything to the PTT line at the radio end

of the cable. If the modem’s internal keying resistor value

is not appropriate for your radio, you should not install the

shunt, but rather install the correct value resistor between

the PTT and Mic Audio lines at the radio interface. Note

that radios specifying a higher value for the keying resistor,

will work with the lower value. Radios requiring an

external resistor are very rare. Note: When using hand-held

radios, it is very desirable to install an external antenna. If

at all possible, the antenna should be located at least ten feet

from the radio and computer. This will prevent the intense

RF field generated by the transmitter from interfering with

the proper operation of the modem and computer.

Warning: Excessively high levels of RF can permanently

damage your equipment.

- CALIBRATION -

All critical functions within the modem are controlled by a

precision quartz crystal and will never require calibration.

Normally, the only adjustment that may be required by the

user is the “LEVEL”adjust on the modem. While this level

has been factory adjusted to the correct level for most

radios, there may be instances where adjustment is

necessary. In such cases, the level should be set to provide

a transmitter deviation of 3.5 to 4.0 KHz. Generally, the

lower deviation level is better. Note that this is less

deviation than would be appropriate for voice

communications. The lower deviation provides superior

phase distortion characteristics for data transmission,

resulting in lower data error rates.

- SOFTWARE CONSIDERATIONS -

Because the RTX-12 is a general purpose radio modem, the

software required for its use will vary according to your

specific application. We have supplied a test program

(RTXDEMO.EXE) on the installation disk that will allow

you to exercise the modem for test purposes. We have also

included sample source code for transmit and receive

routines (RTXSRC.BAS), written in POWER BASIC. This

code is meant only to be a “starting point”for those who

contemplate writing their own software. If you require

extensive software support, Tigertronics may be able to

provide consulting services or recommend a third party

software developer who can meet your needs. Contact our

Tech Support Department for further details.

If you are writing your own software for the modem, the

following basic guidelines should be considered:

Transmit - It is important to remember that it takes some

finite time for the transmitter to become operational after

keying. It will also take some amount of time for the

receiver at the other end of your link to detect the

transmitted signal and open its squelch, allowing audio to

pass to the modem. In addition, the modem requires time to

“lock on”to the signal before decoding begins. As a result,

your software must key the transmitter a moment before

data transmission begins, to prevent data loss. This time

delay is called “TXDELAY”and will vary with the specific

equipment employed. Typical times will be on the order of

300ms.

You must also allow the transmitter to remain keyed

momentarily after data transmission stops, so that the

receiving software sees a clear separation between the end

of valid data and the burst of noise it receives when the

transmit carrier drops and the receiver squelch activates.

We call this delay “TAIL”. It can generally be shorter than

TXDELAY and will normally be on the order of 200ms.

Depending on your specific application, hardware and

software, you may be able to shorten these times

significantly. For instance, if a constant carrier is sent, you

will not need them at all.

Receive - To receive without error, your software must be

able to identify the TXDELAY and TAIL periods.

TXDELAY detection tells your software that data will soon

follow. TAIL detection signals the end of valid data and

warns that a burst of noise will probably appear when the

transmitted carrier drops. In some applications you may

find the “carrier detect”signal helpful in detecting these

events. The carrier detect signal will be “low”when the

carrier is detected and “high”when no carrier tone are

present. Your software should detect a “stable”carrier

signal for some time before processing data.

- LIMITED WARRANTY -

Tigertronics warrants the RTX-12 modem to be free of

defects in material and workmanship for a period of 90 days

from the date of shipment. Tigertronics will repair or

replace, at its option, any parts found to be defective during

the warranty period. This warranty does not include any

unit which has been subject to misuse, neglect, improper

installation or operation. This warranty is in lieu of all

others, express or implied, and no person or representative

is authorized to assume for Tigertronics any other liability

in connection with the sale or use of this product.

Tigertronics will not be responsible for any expense or loss

of revenue or property incurred by the user due to operation

or malfunction of this equipment. Tigertronics reserves the

right to make circuit or component changes, or to

incorporate new features, at any time, without obligation.

- RETURN POLICY -

A Return Material Authorization Number (RMA#) must be

obtained from the factory before any product will be

accepted for return or repair. Items received at the factory

without an RMA# clearly marked on the OUTSIDE of the

package WILL NOT BE ACCEPTED. Items being

returned must be sent prepaid. Returned items should have

a tag attached showing the RMA#, customer name, return

address, phone number, and action requested. Units being

returned for warranty repair must be accompanied by a copy

of the original sales invoice showing the date of purchase.

Customers wishing to return a product for refund, for ANY

reason, must receive an RMA# within 15 days from the

shipping date shown on the original sales invoice.

Customers returning products for refund will be charged a

Restocking Fee equal to 20% of the purchase price, to cover

the cost of re-testing and re-stocking. Products which have

been damaged or modified in any way, may not be

returned. Contact our Technical Support department for the

RMA#.

- TECHNICAL SUPPORT -

Technical Support for this product is available by calling

our Support Hotline at (541) 862-2639 any Monday,

Wednesday, or Friday between 1 PM and 5 PM (PST).

- FCC STATEMENT -

NOTE: This equipment has been tested and found to

comply with the limits for a Class B digital device, pursuant

to Part 15 of the FCC Rules. These limits are designed to

provide reasonable protection against harmful interference

in a residential installation. This equipment generates, uses

and can radiate radio frequency energy and, if not installed

and used in accordance with the instructions, may cause

harmful interference to radio communications. However,

there is no guarantee that interference will not occur in a

particular installation. If this equipment does cause

harmful interference to radio or television reception, which

can be determined by turning the equipment off and on, the

user is encouraged to try to correct the interference by one

of the following measures:

·Reorient or relocate the receiving antenna.

·Increase the separation between the equipment and

receiver.

·Connect the equipment into an outlet on a circuit

different from that to which the receiver is connected.

·Consult the dealer or an experienced radio/TV technician

for help.

Caution: Changes or modifications not expressly approved

by the party responsible for compliance could void the users

authority to operate the equipment. To meet FCC

requirements, shielded cables are required to connect this

device to a personal computer or other Class B certified

device.

TIGERTRONICS, INC.

FCC ID: EVFRTX12

This device complies with Part 15 of the FCC Rules.

Operation is subject to the following two conditions:

(1) This device may not cause harmful interference,

and (2) this device must accept any interference

received, including interference that may cause

undesired operation.

- RTX-12A CONNECTIONS -

Data Connector (DB-25S):

Pin #2 (TXD) - Transmit Data

Level: RS-232 (+/- 15v max)

CMOS (0/+5v typ)

Pin #3 (RXD) - Receive Data

Level: RS-232 (+/- 3v min)

CMOS (0/+4.7v typ)

Pin #4 (RTS) - Negative In / PTT

Level: RS-232 (+/- 4.7v min)

CMOS (0/+4.7v typ)

Pin #6 (DSR) - Carrier Detect

Level: RS-232 (+/- 3v min)

CMOS (0/+4.7v typ)

Pin #7 (GND) - Power/Digital Ground

Pin #20 (DTR) - Positive Supply

Input: +4.8 volts (min)

+15 volts (max)

Current:5 millamperes (typ)

Radio Connector (RJ-11):

Pin #1 (Yellow) - Mic audio

Output Level: 0 - 290 mv p-p (Hi Z)

0 - 80 mv p-p (1K ohm)

Factory Set: 20 mv p-p (1K ohm)

Pin #2 (Green) - Receive Audio

Input Level: 300 mv p-p (nom)

780 mv p-p (max)

Input Z: 50K (typ)

Pin #3 (Red) - PTT Output

Output Level: Sink 50ma (max)

Output Voltage: 15 volts (max)

Output Type: Open Drain (FET)

Pin #4 (Black) - Ground

“HT”Jumper - Connects 2.7K resistor between the PTT

and Mic Audio lines for keying some

hand-held radios. See notes in “HT”

section.

“LEVEL”- Adjustment on modem that adjusts

transmit audio (deviation) level.

- RTX-12OEM CONNECTIONS -

Data Connector (10-pin header):

Pin #1 (GND) - Power/Digital Ground

(Brown)

Pin #2 (DTR) - Positive Supply

(Red) Input: +4.8 volts (min)

+15 volts (max)

Current:5 millamperes (typ)

Pin #3 (RXD) - Receive Data

(Orange) Level: RS-232 (+/- 3v min)

CMOS (0/+4.5v typ)

Pin #4 (DSR) - Carrier Detect

(Yellow) Level: RS-232 (+/- 3v min)

CMOS (0/+4.5v typ)

Pin #5 (TXD) - Transmit Data

(Green) Level: RS-232 (+/- 15v max)

CMOS (0/+5v typ)

Pin #6 (RTS) - Negative In / PTT

(Blue) Level: RS-232 (+/- 4.5v min)

CMOS (0/+4.5v typ)

Radio Connector (10-pin header):

Pin #7 - Receive Audio

(Violet)

Input Level: 300 mv p-p (nom)

780 mv p-p (max)

Input Z: 50K (typ)

Pin #8 - PTT Output

(Gray)

Output Level: Sink 50ma (max)

Output Voltage: 15 volts (max)

Output Type: Open Drain (FET)

Pin #9 - Mic audio

(White)

Output Level: 0 - 290 mv p-p (Hi Z)

0 - 80 mv p-p (1K ohm)

Factory Set: 20 mv p-p (1K ohm)

Pin #10 - Ground

(Black)

“HT”Jumper - Connects 2.7K resistor between the PTT

and Mic Audio lines for keying some

hand-held radios. See notes in “HT”

section.

“LEVEL”- Adjustment on modem that adjusts

transmit audio (deviation) level.

- GENERAL SPECIFICATIONS -

Levels (Radio): Mic Audio - 290mv max (Hi-Z)

Receive Audio - 300mv (nom)

PTT - 15v @ 50ma (max)

Levels (Data): RS232 (+/- 3v min)

CMOS (2.5v min / 5v max)

Power Supply: +4.8v (min), +12v (max) 2.5ma

Operating Mode: Simplex or half duplex

Compatibility: Bell 202 (Opt. CCITT v.23)

Dimensions: Standard: 2.1”x 2.4”x .72”

OEM: 1.25”x 1.50”x .45”

Connectors: Standard: DB-25S / RJ-11

OEM: 10 pin header (.1”cent)

Operating Temp: -30C to +60C

- OPTIONS -

CCITT v.23: Factory installed option to provide

CCITT v.23 compatible input/output tones

(1300/2100 Hz).

Input Level: ** Factory installed option for low input

impedance (ie: 600 ohms) and increased

input level capability (Rx Audio).

Output Level: ** Factory installed option to increase

or decrease output modulation level.

Rx Only: ** Version without transmit components.

Tx Only: ** Version without receive components.

** These options available on quantity purchases only.

Note: Contact the factory regarding special configurations,

such as Transmit or Receive Only versions. We welcome

the opportunity to quote any other special modifications that

you may require.

- MODEL NUMBERS -

Standard: Model RTX-12A, RTX-12OEM

w/CCITT v.23: Add “V23”to part number

(RTX-12AV23)

(RTX-12OEMV23)

Cable for OEM: OEMCAB1

(6”Colored Ribbon w/IDC)

- RTX-12OEM CIRCUIT BOARD DIMENSIONS -

(Top View) 1.250 1.500

1.000

1.250

Mtg. Holes: 4ea 0.120”(#4 screw)

This manual suits for next models

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