Telephone tests at the Post Office Engineering Research Station to determine the percentage of words received correctly.
Dollis Hill, London.
M/S of John Laurie at table talking into microphone. M/S speaker on the wall. M/S man at desk with headphones on taking down messages. C/U girl wearing headphones, camera pans down to notes she is taking. Various shots of John at table taking telephone off stand and fixing another one on. C/U John's face. Various shots of telephone on stand, C/U as John checks adjustments on phone. C/U John's face. C/U code words used in the testing of the phones. C/U as John begins to talk again. C/U sound meter with needle moving. C/U chart and man writing on it, the camera pans up to the man who is wearing headphones. C/U headphones.