Broadcast System

The Mercury 750 series of communication units are robust and versatile self contained loudspeaker stations suitable for use in a variety of applications. These units are manufactured for use in office, industrial and arduous environments such as coal preparation plants, processing plants, power stations and quarries where safety and reliability are of paramount importance. Two versions are available:

The Mercury has a removable self sealing lid equipped with loudspeaker, microphone and two bezelled push button switches with ‘press to call’ and ‘speak’ facility. The unit is supplied in a robust high grade grey finish polycarbonate enclosure to meet IP54 requirements - a flame retardant grade is available on request.

The Mercury Weathermasters are manufactured to the highest standard also using a robust high grade grey finish polycarbonate enclosure fully meeting IP66 requirements. The unit is ideal for use in external or other exposed areas. The cover is equipped with a weatherproof loudspeaker, water-proof microphone and two push button switches giving ‘call’ and ‘speak’ facility, the switches having external neoprene shrouds for an external seal against the ingress of water.

System Operation

The loudspeaker drives through a stainless steel mesh located behind the front panel louvres, providing a high degree of protection from damage and weather. The microphone is designed to eliminate high extraneous background noise such as machinery etc, during conversation between units. These units may be installed as a simple one-to-one basis, providing highly effective communication between two areas, or additional units may be combined to provide communication between additional zones. A wide range of ancillary equipment may be incorporated to provide an entire communication network. In the event of mains failure a battery back-up version is available. A ‘hands free’ model can also be supplied.

Speech is transmitted at a signal level of approximately 1 volt from a low output impedance amplifier, thus ensuring high immunity from interference pick-up in the two core audio cable used between units.

The received signal is then amplified and is capable of driving up to 15 watts r.m.s. into 4 ohm impedance. As the switching is performed by relays in the amplifier, external microphones with ‘press to speak’ facilities can be used.

All versions incorporate a removable chassis to which a lid assembly connects via a multi-pin plug socket. Each unit is supplied with power from a local mains supply at 110/120 volts or 220/240 volts 50/60 Hz single phase a.c.

System Installation

The flexibility of the Mercury system enables two stations to be connected directly to a two core audio cable, or a multi-station complex system connected either in a ring main or in a radial configuration to a manned central exchange unit.

The audio line conductors should be twisted pairs of conductor size 0.5mm2, with the addition of an overall earthed screen when used in areas of high electrical interference on the route taken by the cable.

The mains cable should be capable of safely carrying 5 amperes at 240 volts a.c.

Ancilliary Equipment

Additional equipment is available, which may be used in conjunction with the Mercury broadcast system:

The Calfonex manned central exchange units provide the facilities of controlling all calls made on the system. They may also be used to interface with communications in hazardous areas via approved couplers. Full details of this unit are available from our sales office.

The Deskmaster is designed for use in an office or similar environment. The unit is desk mounted and has all the facilities of the Mercury unit. The output of this unit is 4 watts r.m.s.

The integral amplifier of the Mercury unit is capable of driving external re-entrant loudspeakers for broadcast paging in noisy environments. Alternative loudspeakers are available to suit individual requirements, an 8 ohm extension speaker may be connected individually or two in parallel to each Mercury unit to suit the specific requirements of the customer.

Athos portable handsets may be introduced into the communication line with a separate plug-in jack point to provide two-way communication facility between handsets, or broadcast/call facility to Mercury units on the system. The unit has a high grade polycarbonate enclosure and is powered by an internal dry battery.

Battery Supported Mercury Communication Units

The Mercury 750 series are available with optional battery support either supplied with new units or retrospectively fitted to earlier models.

The batteries are sealed lead acid type and are trickle charged continuously. They are neatly concealed in the lid. Connection to the main chassis is via a plug and socket. The batteries are capable of supporting the Mercury in excess of 48 hours, with occasional use of the transmit and receive functions (approx 10 mins of every hour). For continuous speech transmission or reception the batteries will operate for a minimum of 4 hours. For a continuous emergency tone broadcast through the Mercury the batteries will last for a minimum of 3 hours. After complete discharge where the Mercury will no longer operate the batteries will recharge fully within 36 hours of power restoration.

Battery kits are available for retrospective fitting to existing Mercury installation.

Specifications