Communications (Coaxial)

Coaxial cables are high frequency transmission cables that consist of a centre copper core surrounded by insulation and then a grounded shield of braided wire. The coaxial cable has the capacity to transmit information 80 times faster than the standard twisted pair.

The QEW Mississauga and Burlington COMPASS systems utilized a broadband coaxial system for communications between the central computer system and all field controllers. The coaxial communication system is configured in a "sub-split" design using 5 to 30 MHz as the outbound bandwidth (TOC to remote) and 50 to 300 MHZ as the inbound bandwidth (remote to TOC).

The amplifiers are designed to handle duplex communications for data, voice and television signals within various bandwidth configurations. The control signal data originates at RS-232-C data ports at the TOC and at field equipment stations. The data signals are modulated and demodulated at the appropriate RF transmit/receive frequencies via data modems with the communications subsystem technically transparent to the data protocol.

The television signals are unidirectional towards the TOC and are amplitude modulated and up- converted onto television channel frequencies. The data system includes field modems driving camera control receivers(CCTV), sign controllers (CMS), traffic controllers (VDS, RMS) and master modems in the TOC interfacing with the computers or master controllers. Outbound data for polling or control of field equipment is generally in a low frequency band (near 30 or 120 MHz). Inbound data for reporting field data is generally in a higher frequency band near the CCTV channel frequencies.

See also:

• Traffic Operations Centre (TOC)
• Central Computer System
• Closed Circuit Television (CCTV)
• Vehicle Detector Stations (VDS)
• Changeable Message Signs (CMS)
• Ramp Metering Stations (RMS)
• Field Provisions (ducts, cabinets, footings, power, etc.)
• Communications Subsystems:
  • Fibre-Optic
  • Coaxial