WHARTON 4850.T.S.UK MASTER CLOCK Free standing

A master/slave clock system manufactured in the UK by Wharton Electronics, using its own time code system to drive the slaves, a code capable of being sent long distances over standard unscreened two-core wiring. Clock displays operate as slaves or in stand-alone mode.

The 400A series of clocks, calendar clocks and world time-zone display systems provide a precise and elegant display of time, or time and date, using bright and clear red or green LED characters with both manual and automatic brightness control. 400A series clocks are normally powered from a mains supply, an automatically recharging internal battery provides a standby supply to maintain the time keeping in the event of an interruption in the mains power supply. Low voltage operation is available as an extra cost option.

All may be used either as stand-alone units, operating from their internal high stability quartz crystal oscillator or as slave clocks controlled by one of a variety of signal sources. Additionally, the 401A, 420A and 490A series clocks may be used as stopwatches or elapsed time counters when controlled by a type 496A external switch unit.

The 400A range are supplied in rectangular cases suitable for surface mounting on a wall, flush mounting in a panel or with a mounting box for installation in a solid wall. Ceiling suspension of single and double sided units is available.

Some of the more popular types are held as stock items, but others are available to special order, on short lead time. Special application versions are not listed below but details are available on request. Clocks may be supplied with different case colours and finishes to special order. Special outer cases, providing protection to IP65, can be supplied for use in difficult environmental conditions. The various display formats are available in a wide variety of sizes with character heights from 14mm to 200mm and suitable for use at maximum viewing distances from 14 to 120 metres.

Master Clocks

All 400 series clocks and calendar clocks may be used either as independent units, maintaining timekeeping from their internal high stability quartz crystal oscillator or as slave displays with time-keeping derived from an external master clock. Two types of master clock may be used. The first is an impulse master clock, normally used for controlling analogue slave clocks. The impulse master clock provides control by means of impulses every second, half minute or minute. The principal disadvantage of this type of control is that each slave clock requires accurate initial time setting and will display an incorrect time for up to one hour during seasonal time changes.

Alternatively, a 4850 digital master clock may be used, which produces a low voltage digital time and date serial code (called W482) which will directly control up to 50 slave displays. The W482 time code output is intended to control 400A series displays and clocks operating in slave mode and displaying time, or time and date, in up to fifteen different time-zones and can be pre-set to provide an automatic seasonal time change with different dates and time for each of the fifteen time zones. This code is a low voltage (12V nominal), 50 bits per second digital time and date signal that has almost total immunity to external electrical noise. Digital clocks and displays may be driven at distances of up to 1km using a non-critical, unscreened, single cable pair transmission link. It should not be confused with SMPTE/EBU time code - they are completely different types of code.

All time setting is carried out centrally at the master clock; an additional slave display will automatically show the correct time within one minute of being connected to the system. Following a power failure all slave displays will show the correct time within one minute. Time and date code is not transmitted during power failures as the slave clocks are automatically corrected when power returns.

The 1U 19-inch rackmount, 4850 master clock provides the proprietary W482 code, as well as RS232, RS422 and RS485 outputs, programmable relay contacts and an RS232 “on-time” signal as standard and can be optionally supplied with EBU/SMPTE timecode, to allow communications with computers and broadcasting equipment. Free software is provided for use on Windows NT4 (x86) and Windows 95/98 platforms for synchronisation purposes.

Serial time and date information can be supplied in ASCII format to RS232, RS422 and RS485 standards, which can transmit in one of more that twenty different serial ASCII time and date telegrams at user selected intervals. General purpose formats are user configurable for 7 or 8 data bits, odd, even or no parity, a baud rate of 1200, 2400, 4800 or 9600 and message repetition rates of every second, minute, five minutes, hour, day or on request. A single pulse per second, “on-time” signal output is also available to RS232 precision.

Relay changeover contacts can be programmed to show a changeover for one second every 5 seconds, one minute, hour or once per day at a programmable time. They can also be used to changeover in the event of a power failure, an error state or when locked to an external time reference. The conacts are rated at 30V DC @ 500mA.

The standard internal high stability quartz oscillator has an accuracy of ± 0.1 seconds per day at 20-25°C. If synchronised with the 488GPSB receiver system (available separately), the RS232 “on-time” pulse per second is maintained to within 50 microseconds. Optionally, this can be connected to a 484 series radio time-code receiver to enable the internal time-base to be synchronised with the signals transmitted from MSF (Cumbria, UK - formerly from Rugby, UK) or DCF (Mainflingen, West Germany). When synchronised to either signal the master clock time will typically be correct to within 30 mS of UTC (Universal Time Code).

Optional output modules

SMPTE/EBU time code: For broadcast applications an SMPTE/EBU time code may be supplied with hours, minutes, seconds and frames (1/25 second) information. The output is balanced low impedance or 600 ohm at nom.+ 10dBm (adjustable).

Power source

The 4850.R (rack-mounting) will operate from a 230V AC source, 50Hz, with IEC inlet, (no lead supplied). The 4850.T free-standing version is supplied with a plug-in power supply.

Radio time code synchronisation

The radio time code synchronisation option permits 400A series clocks and master clocks to be automatically synchronised with the time code information transmitted from radio station DCF located at Mainflingen near Frankfurt, West Germany, or MSF at Cumbria, UK. The DCF signal is transmitted at 77.5kHz and is derived from an atomic clock at the Physics Institute of Brunswick. The MSF signal is transmitted at 60kHz and is referenced to the Caesium Beam Oscillator at the National Physical Laboratory.

The type 484.02 (MSF) and 484.03 (DCF) time signal receivers are housed in a compact weather-proof case and are connected to the clock display (in the case of single clocks) or master clock (in the case of clock systems) by a single cable pair connection. In many locations the receiver will operate within the building. In difficult reception areas, where an external mounting point is required, the receiver unit may be located up to 200 metres from the clock.

The type 484.06 (MSF) and 484.07 (DCF) low-cost time signal receivers are for indoor use only. These have uni-directional aerials, and also are for use with both clock displays or master clocks.

The received and decoded signal provides an operating accuracy of better than ±0.005 seconds, and provides completely automatic seasonal time changes. In the absence or corruption of the signal, the individual clock or master clock will maintain timekeeping using its internal high stability quartz crystal. On the resumption of reception the clock or master clock will automatically re-synchronise with the transmitted code.

GPS (Global Positioning System) synchronisation

GPS is a system of 21 satellites in six orbits, each orbital plane equally spaced about the equator and inclined at 55°. The satellites transmit highly accurate, real-time worldwide navigation information at a frequency of 1575.42 MHz that anyone with a suitable GPS receiver can use to identify their position, together with a precise UTC time. The GPS system was developed by the US government initially for military use and is now available for unlimited commercial access. It is ideal for broadcast locations, out of range of MSF or DCF radio code transmissions, where international time accuracy is required.

GPS satellites travel in nearly circular orbits every 12 hours at an altitude of 20.183km (10,898 nautical miles). The exact position of each satellite can be determined at all times. Each satellite continuously transmits a unique code sequence, derived from atomic clocks, which is tracked by the GPS receiver. The transmitted information includes current orbital data for each satellite. The GPS receiver is able to identify each satellite by its code and is able to calculate the satellite’s exact position in space.

From this satellite position information the time between the signal transmission and reception is determined. The GPS receiver uses the calculated information to determine its distance from several satellites. The receiver then uses a process called triangulation to compute its own position together with a precise UTC time.

The Wharton 488BGPS receiver system is designed to allow 4850 series master clocks to be automatically synchronised from the GPS satellite time transmissions. The system comprises a low-profile disc shaped active antenna module, 10cm diameter and 3.5cm high, specifically designed for GPS use. GPS signals are amplified within the antenna assembly and then relayed to the GPS receiver module for processing. A protective housing shields the antenna from wind, rain and snow.
The GPS receiver/decoder module contains an advanced Motorola 8 channel parallel receiver, a power supply and a microprocessor based communications interface. To ensure ease of operation and to remove the possibility of operator error the 488BGPS system is designed to self initialise without the necessity of operator data input. On power-up the receiver will automatically begin to search the sky for all available satellites. After three satellites have been acquired a precise date and time will be calculated from the satellite data transmissions. When the accurate satellite time information is available, synchronising time signals are transmitted every minute from the receiver/decoder module to the master clock using W482 time code. This code provides UTC time and date information and may be used to synchronise any 4850 series master clock. The code may be transmitted up to 1000m using an unscreened twisted cable pair.
The 4850 series master clock will automatically convert the UTC time to local time using operator pre-programmed time offset corrections. The time offset value may be automatically changed to allow for seasonal time changes at the appropriate dates according to European, UK or USA requirements. The seasonal change-over dates may be pre-programmed in the master clock up to one year in advance. When the 4850 master clock is synchronised with the GPS receiver/decoder module all transmitted signals are accurate to within 50 microseconds of UTC.

Clock displays

Units are 220/240V powered (except 490A.01 which are 9-12VDC), the automatically re-charging internal battery will maintain timekeeping in excess of 24 hours when fully charged. Cases are constructed from aluminium extrusion and sheet. Cases for surface mounting are supplied with mounting brackets which permit the face to be vertical or at 3° or 6° from vertical. Flush mounting units are supplied with brackets suitable for flush mounting in a panel with rear access. A semi-recessed connector block is incorporated at the rear. Display brightness intensity is variable, with a choice of preset levels. Calendar clocks can display the date using one, two or three selections from 21 languages (including Russian), with the ability to display alternative languages sequentially automatically. Other languages may be available to special order.

Standard surface-mount clocks have black anodised case, panel-mount black anodised; both have red characters. Other case, or green character versions are available to special order, generally on short lead time.
The following operating modes for the clock displays are user selectable:

• 12 or 24 hour time display format
• Stand-alone operation
• Operation from an impulse master clock with either uni-polar or polarised impulses of 6-24 volt amplitude and at one of the following rates: 1 second impulses, 1/2 minute impulses, 1 minute impulses. Loading 7mA at 24 volts.
• Operation from a 4850 master clock with the displayed time selected from one of fifteen different time zones.
• Synchronisation with the radio time code signal transmitted from either MSF (Cumbria) or DCF (Mainflingen, West Germany) when used with a 484 series radio code receiver head unit.
• Automatic control or one of seven pre-set levels for display brightness.
• All models may be programmed to provide an alternating time/temperature display (requires 406 sensor).
• IRIG-B or Afnor NFS87500 time code signals - requires optional type 404.I internal interface.
• Synchronisation from a SMPTE/EBU time code signal or up down slave operation from 414 production timer - requires option 404.E internal interface.
• Note that ONLY ONE of 404.E or 404.I modules may be fitted in the accessory slot within each clock.
• The 401A, 420A and 490A series of clocks may be operated as stopwatches or elapsed time counters when used in conjunction with a type 496A switch control unit.
• Catalan, Croat, Czech, Danish, Dutch, English, Finnish, French, Gallician, German, Hungarian, Italian, Norwegian, Polish, Portuguese, Russian, Spanish, Swedish or Welsh languages for the week and month with the ability to display any one, two or three languages at user pre-set intervals.
• In the event of a power failure the internal batteries maintain timekeeping (but do not operate display) for over 48 hours.

When used in conjunction with a master clock the slave display requires a data connection in addition to the connection to the local mains supply. All displays are normally connected in parallel to the master clock using a single cable pair data link. The specification of the interconnecting cable is generally non-critical and twin 1.5mm² is the standard recommendation.

Operation

The 401A, 420A and 490A series of clocks may also be operated as stop-watches (instead of clock displays) or elapsed time counters when used in conjunction with a type 496A switch control unit. The following display resolutions are user selectable:

The 496A switch control unit is intended for manual operation. Facilities are provided for start/stop display, hold or ‘freeze’ and reset operations. The start/stop control may be used for single event timing either on a continuous or interrupted basis. The display hold control permits the recording of a series of sequential times. Alternate switch activations stop and restart the display while the internal counter continues operation.

Master Clock Ordering Options

The 4850 Master Clock is available in two formats, rack-mounting with internal power supply, and free-standing with plug-in type power supply. As standard it provides W482, RS232, RS422/ RS485 code outputs, an RS232 precision 1pps “on-time” signal, a programmable changeover relay contact pair and is fitted with a high stability quartz crystal oscillator. It can be supplied optionally fitted with EBU/SMPTE timecode output, or with a multi-standard IRIG code output. The optional -IRIG interface provides a 1KHz amplitude modulated signal via a transformer coupled output. The output signal level is internally adjustable 0-7v p-p and is factory preset to 3v p-p. The output signal format may be selected by the user from the following choice:

• IRIG-B (B123)
• IRIG-E (E123)
• Afnor NFS 87­-500
• NEMA 911
• IEEE 1344 (limited implimentation)

Note that satellite and radio code receiver heads are ordered separately as required.

Display Clock Ordering Options

Interface boards, eg. 404.E - SMPTE/EBU timecode input, are supplied separately for user fitting, and should be ordered separately as required.