OBOE required two transmitting stations, one codename CAT which transmitted a series of dots and dashes each side of an arc which ranged over the target. The other station, codename MOUSE, plotted the aircraft's position along the arc until it reached the point where it was instructed to release its load.
The pilot had to fly along the arc guided by the dots and dashes. If he was on track he would hear a continuous note but this would break up into dots if he drifted or dashes if he drifted away. The system could only be used by one aircraft at a time, range is over 250 miles from its most distant ground station and an accuracy within 100 yards.
The OBOE system was specially for the Havilland Mosquito pathfinders, who dropped marker bombs for the following Lancasters.| Use | |
| RAF designation | ARI 5148 ARI 5513 |
| Main items | Receiver R3564 or 3189 |
| Frequency | P-band |
| Remarks |
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| Use | |
| RAF designation | ARI 5582 ARI 5514 |
| US designation | AN/APS-2 |
| Main items | Receiver R3540 (RT-4/APS-4) |
| Frequency | S-band |
| Remarks |
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OBOE test equipment
| TS 222 | |
| wavemeter | TS 223 |
| wavemeter | TS 224 |
| wavemeter | TS 244 |
| fld st | TS 85 |