There are broadly two methods of reaching that data. The first is over telecom lines; the second is over power line carrier (PLC) systems installed on high-voltage lines, or over OPGW systems. In the second method an FSK (Frequency Shift Key) modem is used — converting RS-232 into the system interface and allowing transmission at different frequencies on the same line. These modems carry IEC 870-5-101 serial data at speeds between 200 and 1,200 Baud. The receive and transmit levels, frequency and speed of the modem can be changed as required.
The three FSK modems used in Turkey
DCE IG202T-R38Siemens FWT2000iABB RTU560 chassis-mounted FSK modem
DCE IG202T-R38
A multi-standard modem transmitting asynchronous and transparent data in the 300–3400 Hz voice band. At low speeds it uses binary frequency shift keying (FSK), which is least affected by errors in the band in use and provides communication over long distances. At high speeds it uses QAM modulation with 4, 8 or 16 signal constellations depending on the selected rate.
- Voice band
- 300–3400 Hz, asynchronous and transparent data
- Standards
- CCITT V.29, R.38A, R.38B, R.37, R.35, V.23, BELL 103, BELL 202 2400 Bd, Cegelec 1200/600 Bd
- Operating mode
- In FSK mode half or full duplex, point-to-point or point-to-multipoint; receive and transmit channels can be set independently
- V.29 mode
- 4-wire full/half duplex as standard
- Processor
- Texas Instruments 32-bit DSP — programmable, offering high service flexibility
- Configuration
- Via AT commands over the front-panel Diag port; firmware upgrades use the same port
- Application
- Designed for SCADA infrastructure in power generation networks; works over private, leased, radio and power lines depending on the selected mode