[ Self Contained Payphones.]
            iNFERNO oF MED&eLTECH

 The following is from an aging BT document on Payphone on-site maintenance, 
the document is fairly old to it may not be that relevant today.. 

CODE FUNCTION OF TEST 

Operational Tones 

07 400 Hz Coin Tone 
08 800 Hz Identification Tone 
09 1200 Hz Identification Tone 
10 400 Hz Warning Tone 
11 400 Hz Coin Tone (Reciever short circuit) 

MF 4 Tones 

12 679 Hz Reciever Short Circuit 
13 770 Hz `` 
14 852 Hz `` 
15 941 Hz `` 
16 1209 Hz `` 
17 1336 Hz `` 
18 1477 Hz `` 
19 1633 Hz `` 

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