Dedicated telephone lines are excellent means of transmitting and receiving telemetering signals. While these lines are part of the public telephone system, they are not connected to the public dial-up telephone system and are dedicated to full time telemetry use. The lines are normally provided at 600 ohms impedance and attenuate voice band signals at a rate of 1db per mile. Telephone engineers can design a dedicated system to meet any telemetering requirements.

The public dial-up telephone system carries voice band signals. Da-Tel’s telemetry signals are voice band signals and may be carried over the public dial-up system, with certain level restrictions. Fax machines carry their messages at a reduced level as do typical computer based dial-up modems.

Da-Tel’s model G-9813 Telco Interface Module allows the telemetry system to be interfaced to the public dial-up telephone system. For example, the power flowing into a factory, the water level at a reservoir or gas pressure in a pipe can be measured for the price of a phone call. Da-Tel’s digital telemeters hold last data. The G-9813 has been registered with the FCC part 68 code, Permit #IDF USA-36002-OT_N.

In general, radio connection telemetering should not interfere with voice communications because the radio frequency carrier should not be left on except as needed for use. Since the FCC controls the use of radio frequency channels, a telemetry channel can be either a dedicated licensed channel or a spread spectrum type unlicensed channel. A license is preferable for a long time installation. Diagrams may be obtained from the factory showing the use of our digital telemeters, which hold last data over a wireless radio connection.

Da-Tel models G-2001 Fiber Optic Parallel-to-Serial Transmitter and G-2002 Fiber Serial-to-Parallel Receiver can send and receive 16 status points over a single or multi-mode dedicated fiber. The system uses Manchester encoding to transfer the clock, sync and data over the glass fiber and a parity bit generator checks the data for errors.

Da-Tel models G-2003 Fiber Optic Digital Telemeter Transmitter and G-2003 Fiber Optic Digital Telemeter Receiver incorporate a 10-bit A/D message using the same Manchester encoding technique. The 18 bit message also has 6 address/status bits and 2 sync pulses. When more than one analog quantity is required, up to 64 scaleable analog points may be monitored when these modules are used in conjunction with the G-7903 Analog Input Module (8 inputs per module) and G-8404 Quad D/A Module (4 Outputs per module). At 15.36 Kb/s the update time per analog measurement is 8.8ms.

A dedicated fiber optic line offers very high voltage isolation from lightning to ground planes in substation applications. Being immune to lightning protects communication equipment on both ends of the line from electrical discharges. Tampering and security problems are also minimized by the use of fiber optic lines. Perhaps the greatest advantage of fiber optic cable is that it is dedicated to your use only. A dedicated fiber optic line in the most secure means of data transmission available today.