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JED communications interfaces:

  • J995X & A: JED RS232 to RS485 (& RS422);
  • J990: RS232 to 20mA converter;
  • J994: Midi to RS232 conv;  
  • T462: Weigand to RS232;
  • J998: RS232 multiplexer

JED 995X photo

JED J995X RS232 to RS485 converter

1. JED RS232 to RS485 converter, J995X, with automatic "TX connect-to-line" function for the transmitter, so it does not need special driving software to transmit from a PC to a multi-drop RS485 line. This is ideal for operation from Windows and other software which has difficulty in accessing the driving logic behind the RTS line drivers.

Links provide for baud rate selection, transmit byte length selection, RX line biasing, line termination, and optional RX blanking during transmission.

A recent software revision allows the transmitter to be always enabled, so for 4-wire operation, with one pair always transmitting and one pair always receiving, a two way long distance data communications channel can be set up, equivalent to RS422 standards.

A data sheet is at: J995X.pdf (101KB). A close-up photo is at J995X.jpg, (34KB). It is priced at $A160 (plus $A16 GST). An optional 9 volt plug pack is $A20 (plus $A2 GST).

2. JED J995A, our original RS232/RS485 converter, which uses the RS232 RTS line going HIGH to turn on the RS485 transmitter.

Links provide for RX line biasing, line termination, and optional RX blanking during transmission.

The data-sheet is at: J995A.pdf (54KB). The photo is at J995A.jpg (25KB). This unit is priced at $A140 (plus $A14 GST).  An optional 9 volt plug pack is $A20 (plus $A2 GST). See National Semiconductor's application notes for RS485 via link: National Applications.

(JED makes a number of other RS232 and TTL/CMOS to RS485 converters, with various power options and I/O options (B, C, D, E, F......) Call JED for specific requirements...we can probably do it.)

3. JED RS232 to 20mA isolator, J990, a bi-directional interface from a PC to a 20mA signalling loop. This is useful for interfacing to PLC and other industrial systems from a PC or terminal. While this is an old standard, it is still in occasional use, and JED still supports it with this box.

The data-sheet is at J990.pdf (105KB). A photo of the J990 is at J990.jpg, (30KB).

4. J994 Midi to RS232 converter:

This takes RS232 signals (on a D9 connector) at 38400 baud and converts to an opto-isolated Midi signal at 31250 baud. 

994 din end

994 RS232 end

The three Midi connectors are standard Midi 5-pin DIN circular, with "Midi-In", "Midi-Out and "Midi-Thru" provided, allowing the usual daisy-chained Midi "network": This unit is housed in the same case as the PROM Programmer, but in black. All I/O lines are ESD protected and power input from a 9 to 15 volt DC plug pack powers the device. LEDs show the communications in and out for checking purposes. See: 994 Layout pdf

5. T462 Communications/relay box as Wiegand to RS232 converter.

This device receives Wiegand contact closure bit streams and converts to an RS232 message.

T462Applications are to interface an old-style magnetic key (encoded as a series of pulses using embedded magnets) to an RS232 signal to feed into more recent security or communications devices. (The Wiegand interface is also used on more recent RFID and other scanners, as it is a standard used in the security industry.) The T462 is shown on the JED projector controller page.  The case is 12.5cm (inc. connectors) by 5 cm by 2.5 cm.

See:  and

See: for T462 info.
The T462 box can be used for all sorts of usefull comms to/from real-world I/O interfaces. It has four inputs and four outputs which can be loaded with FETs, transistors (in and out) or voltage divider and series resisotrs, or even IR and Dallas 1-Wire  inputs and opto-isolators (by 4). It can be loaded with a DIP-switch and RS485 coms as well. 

The CPU is an Atmel ATMega32. Contact JED with your weird applications!

6. J998 RS232/RS485 Communications Multiplexer.

This device is a small CPU board able to be user programmed as a multiplexer/de-multiplexer for 6 x RS232 or 5 x RS232 and one RS485 channel.

The CPU is an Atmel  ATmega128 (with two UARTs on board) and two aditional dual uarts (ST16C2550) provide four more communications channels.

The communications interfaces are all ESD and EMC protected, and there is a LED by each channel driven from CPU ports as a status indicator for each channel.

A program is available doing 5 to 1 multiplexing with Xon-Xoff  or hardware handshaking.

Power is a DC input  of 9 to 24 volts. The unit mounts on a DIN rail aluminium extrusion box with screwed on end-plates, or can be supplied as an unmounted board.

The unit is 10.5cm by 7.5cm by 3cm high.