GB852633A - Improvements in or relating to electric alarm arrangements - Google Patents

Abstract

852,633. Protective arrangements; electromagnetic relays. REYROLLE & CO. Ltd., A. Dec. 18, 1956 [Dec. 23, 1955], No. 36962/55. Class 38 (5). [Also in Group XXXIX] In an electric alarm arrangement for use at a control station of an electric installation, the operating coil K of a relay in response to an initiating signal (e.g. a fault) is energized to move its contacts to the operative position (Fig. 2) to cause an alarm device H to give a warning indication (e.g. a flashing light), and in response to an acceptance control operation is de-energized to allow some of its contacts to revert to the normal position whilst the remaining contacts J<SP>2</SP>, J<SP>7</SP> remain latched in the operative position (Fig. 3) whereby the alarm device H is caused to give an action indication (e.g. a steady light), the latch K<SP>1</SP> being released in response to a reset operation to allow the remaining contacts to revert to the normal position (Figs. 1 and 4) and reset the alarm device to normal. In the arrangement of Fig. 4 the closure of initiating contacts G causes the operating coil K and an alarm bell B to be energized from bus-bars A<SP>1</SP>, A<SP>2</SP> over the contacts J<SP>2</SP>, J<SP>3</SP>. This causes the position of the contacts to be changed to the position of Fig. 2 so that a holding circuit for the coil K is completed from a bus-bar C<SP>1</SP> over the contacts J<SP>1</SP>, J<SP>2</SP>, J<SP>3</SP>, and a .lamp H is connected over contacts J<SP>9</SP>. J<SP>10</SP> to a bus-bar E<SP>1</SP> energized intermittently by means of an interrupter device E. The contacts J<SP>2</SP>, J<SP>7</SP> are latched so that when a " accept alarm" control switch C is opened and the coil K and bell B are de-energized, the relay contacts assume the position of Fig. 3. In this position the contact J<SP>3</SP> is isolated so that the coil K and the bell B cannot be re-energized and the lamp H is disconnected at contact J<SP>9</SP>, J<SP>10</SP> from the bus-bar E<SP>1</SP> but is connected over contacts J<SP>8</SP>, J<SP>7</SP> to the bus-bar A<SP>1</SP> so that the lamp H gives a steady light. When the latch is released, the contacts revert to the position of Figs. 1 and 4 and the lamp H is extinguished, it being disconnected from the bus-bar A<SP>1</SP> and connected to a test bus-bar D<SP>1</SP> over contacts J<SP>7</SP>, J<SP>8</SP>. The latch may be mechanical or magnetic and may be released manually. Alternatively a latch coil may apply or release the latch electromagnetically in which case the arrangement may be such that the latch is released automatically on the opening of the initiating contacts G, i.e. on removal of the fault. Each section of the installation would be provided with a relay and alarm device H, the bus-bars and bell being common to all the sections so that a blocking rectifier L is associated with each relay coil to prevent interaction between the relays.