BLOCK BELL EQUIPMENT

The Block Bell Equipment is a part of the block instrument which is provided at the end of the block sections at cabins / ASMs. DC impulses cannot be sent in AC electrified area since block circuit is converted from overhead alignment to underground cable terminated as terminating transformer at both of the ends. This Equipment is used in AC electrified area to convert the DC impulses to AC at the sending end and AC impulses to DC all the receiving end. The Equipment is a single transistor oscillator to give 45V AC across 1120 ohms. This also has a full wave rectifier circuit to rectify the received AC Voltage and to energize a relay. The plunger is connected to Terminals TS9 and TS10 of terminal strip (Refer Circuit diagram enclosed). When the plunger is pressed 12 VDC supply is fed simultaneously to the Transistor Oscillator and the Relay So/2. The output of the oscillator, Viz, 45 Volts at 150 Hz, is thus made available at terminals. TS3 and TS11 through the energized contacts of Relay So/2. This is fed to the line. At the distant station, this voltage from the line is fed to terminals TS3 and TS11 at the Block Bell Equipment installed at the station. Though the normally closed contacts of Relay So/2, this voltage is fed to the bridge rectifier. This rectified voltage is available, as desired from terminal TS4 and any of the other terminals, namely, TS5, TS6, TS7, TS12, TS13, TS14 and TS15 for ringing the bell. When the plunger is operated, the single transistor is energized of the Oscillator gives an output 60V (open circuit) @ 150 Hz and 45V (across 1120 ohms) at 50 Hz, sinusoidal at TS3 and TS11.

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