robert-ainsworth documents

Telephony Slide 1 ear T R mouth DTMF ringer C dial switch SLIC Telephone Subscriber Line CO (Local Exchange) cradle switch off-hook on-hook tip (+) ring
Documents Telephony Slide 1 ear T R mouth DTMF ringer C dial switch SLIC Telephone Subscriber Line CO (Local Exchange) cradle switch off-hook on-hook tip (+) ring