What is a KOD-RS? The key on data device is an EIA/RS232 accessory that connects to a wireless or wire-line modem data port and provides Request to Send (RTS) control for the modem from the incoming data. The KOD-RS is transparent to the data and is full duplex with selectable transmit delay.

How Does it Work? When data is received at the KOD-RS input, that data are stored in a First-In-First-Out (FIFO) buffer. At the same time, the RTS line is raised keying "ON" the wireless modem's transmitter. The FIFO will delay the data long enough for T/R synchronism to occur before allowing the output of data. When data are clocked out of the FIFO buffer, the RTS line will drop after a short delay , turning  "OFF"  the modem's transmitter.

How is the KOD used? In replacing a SCADA system's leased phone lines with digital wireless, major data interface problems can occur. Many times, the Data Terminal Equipment (DTE) does not support the send control function. Or it operates in a way that will not allow for proper communication. The sequence required by the wireless modem's transmitter is usually managed by the Request to Send (RTS) and the Clear to Send (CTS) control lines at the EIA/RS232 data port. Typically, when the RTS line is raised the transmitter is keyed "ON". The CTS will wait until the receiver at the other end has time to synchronize, then the CTS will become valid, allowing data to be sent. If the DTE supports only data, then an external substitute for the RTS control mechanism -----the KOD-RS----- is needed.

Another Example: When "smart modules" in a master/slave application are used with wireless for remote sensing applications, the KOD-RS is the best solution for preventing transmitter "burn-out". In a typical Security system that monitors building entrances and exits, a slave "smart module" will scan door switches for status. That information is sent to a master-module which will show the status of switches. Because the scan may be infrequent, once per second, minute, hour or on a status change, the wireless modem's transmitter can fail when keyed  continuously "ON" (Transmission should occur only when the data are present). Because many "smart modules" simply send data, the KOD-RS provides the keying function for the transmitter control.

Description: The KOD-RS uses standard DB25F/M connections; it has selectable delays from 3ms to >12ms.; the ability to pass high-speed data speeds to 38.4 Kbs; low power---less than 50ma at +9 to +12 Volts and a compact size (4"x2"x.75").

The DATA INPUT is at pin #2 of the DB25F connector. The delayed DATA OUTPUT is on pin #2 and RTS is on pin #4 of the DB25M connector. Pins #3, 5, 6, 7, & 20 are wired connector to connector. Power is applied at pin #6. (CAUTION: There are no isolation diodes in this line and a conflict can occur with the DSR of the DTE. Remove power from the DCE before shutting down the DTE.) The common is  pin #7.