Yes the safest way is to use syncronized timers at each timing location and download the time of day splits with bib number ID into a program like was suggested before.
ALGE TED 400 are really good if you use the tone system to check signal.
Be prepared to move the RX receiver around until the tone locks in solid.
Run a banana plug jumper any distance from the RX receiver to the Timer and you are all set.
Sometimes I have to climb trees or telephone poles to get signals.
Always move the RX receiver first! It has more success than trying to move the TX transmitter