Decca Trisponder R02 Distance Measuring Unit, 8-channel, by Del Norte Technology. Top of case has BCD output, power and transponder sockets and an open/close air pressure equalizer. Object has 2 LCD displays marked Display 1 and Display 2 each with knobs marked 1 to 8 . The left LCD is labelled high, battery, low and the right LCD is labelled feet, TSA, meters. The centre buttons are reset and range. The front panel has 8 lights, 8 knobs maked channel/bypass and 8 phillips screws marked range/calibrate. The bottom left has a mode knob marked rapid/normal and a power knob to regulate intensity. The bottom right has a knob marked ranging with man ext/ timed/ time share and auxilliary options.
The basic trisponder system is composed of a distance measuring unit (ZBA 5029), a master station and two remote stations. Each station is a combined transmitter and receiver. The master station has an omnidirectional antenna, and each remote station has a directional antenna. With the remote unite places over stations of known geographic positions, ranges are observed at the distance measuring unit. These values may be plotted manually on a hydrographic survey sheet or converted by trilateration methods to position values.
Coded bursts of microwave frequency (X-band) energy are transmitted from the master unit to each remote unit for a determination of range distances. These units are received and decoded by each remote unit, but only the unit with the particular code is triggered to send back an identical burst of energy to the base unit. The time the signal takes to make the round trip minus electronic delays for decoding is converted to distance using the velocity of X-band energy in the atmosphere? Round trip distances are divided by two to obtain the displayed range distances. At microwave frequencies, the system is limited to line of sight distance measurements.