ABB 23WT25 Modem 50-2400 baud rate serial communication

Applications

The 23WT25 modem is designed to operate on remote control lines with the RTU560.

However, it can also be connected to other data terminal equipment because it operates on an interface similar to a general purpose FSK modem in the voice band.

Because it operates on an interface similar to a general-purpose FSK modem in the voice band

range (300-3400 Hz) of a general-purpose FSK modem.

The 23WT25 modem can be assigned a two-wire or four-wire line with communication channels from 50 baud to 2400 baud (24 channels at 50 baud).

Baud (24 channels of 50 baud, 12 channels of 100 baud, 6 channels of 200 baud, 2 channels of 600 baud).

(12 100 baud channels, 6 200 baud channels, 2 600 baud channels, 1 1200 baud channel).

The modem 23WT25 is available in two versions (rubrics):

- R0001: 5 VDC power supply

- R0002: 24 VDC power supply

Features

The 23WT25 modem enables high-resistance interleaving on multidivision lines. No special additional provisions are required for duplex and half-duplex operation.

such as butterfly connections based on channel assignment and the selected two-wire or four-wire line. It is designed for the transmission characteristics of local cable lines.

Light-emitting diodes indicate the most important operating states, and disconnect test sockets on the front panel make it easy to test and measure VFT channels as well as Data Terminal Equipment (DTE) interface signals.

In the RTU560 subrack, the modem board occupies one slot. The modems are available in two different sizes for two different supply voltages.

In the RTU560 subrack, it is powered by 24 V DC (R0002). the R0002 (24 V DC) can also be used with a 24 V supply voltage with a voltage tolerance of ± 20 %.

Therefore, it can also be used outside the RTU 560. If only 5 V DC is available, the R0001 standard is used.

The digital signal processor (DSP) is responsible for converting binary information into speech bands and vice versa.

Among other things, its high processing power enables highly selective channel filtering (90 dB) and thus unlimited channel assignment.

Channels can be assigned on a CCITT raster basis. The transmitter and receiver can be configured for different baud rates up to 600 bits/sec.

If all channels need to be used in any combination and baud rate, high channel selectivity needs to be configured.

Perform the configuration. Normal selectivity can be used for separate allocation of transmit and receive channels (block configuration and distance of at least one channel between blocks).

Transmission time and isochronous distortion are lower with normal selectivity.

The 23WT25 modem monitors the isochronous distortion of the received signal and indicates the limit (40% or 50%) that is repeatedly (10 times) exceeded by the “Signal Quality Level (SQL)” alarm.

The LED SQL indicator will show at least 4 seconds when the maximum distortion is exceeded, and correspondingly longer for higher interference.

The audio carriers are monitored via the DCD signal and alarmed separately. For multiple transmission lines, the carrier interrupt signal can be delayed by means of an alarm relay.

The delay time depends on the baud rate. The modem's alarm relay reacts to carrier interruptions (DCD direct or delayed), SQL alarms or supply voltage faults.

To compensate for line distortion on critical transmission links, the 23WT25 modem offers adjustable pre-distortion.

Depending on the quality of the transmission link, the pre-distortion can be set from 0 to 10 dB high pass or low pass.

The two 23WT25 modems in the transmission link can be configured as a test transmitter and a test receiver, respectively, to adjust the correct pre-distortion.

The results of the utilization of the transmission test pattern are displayed on the LED EQZ. The blinking frequency of the LED EQZ is the degree of improvement achieved.

The 23WT25 modem connects up to three star-coupled transmission lines as point-to-point links without repeaters.

The transmitter output circuit operates as a constant current source.

All basic settings such as channel, gain, line operation mode, line termination, and transmission rate are configured by jumpers.

The serial interface signals of the Data Terminal Equipment (DTE) as well as the VFT line can be measured or turned on using the disconnect test socket on the front panel.

If higher isolation voltages are required, an additional VF signal transformer must be used.