Technology AUDIO FREQUENCY TRACK CIRCUITS

1. Types of A.F.T.C. TI-21 (ABB)‏ FTGS ( SIEMENS )‏ ALSTOM (DC-CODED)‏ UM-7 SEF- FRANCE 1699 Hz 2296 Hz 1996 Hz 2593 Hz 1549 Hz 2146 Hz 1848 Hz 2445 Hz 8-TYPES FTGS-46…