In some sites it is necessary to use modems to connect the remote clocks to the computer system. This document details factors that should be taken into consideration when deciding if the computer should dial the clock, or if the clock should dial the computer.

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Phone Line Costs

Probably the most significant item to consider is the cost of dedicated phone lines. If the Clock dials then the PC will need a dedicated incoming phone line. It has to be dedicated because if the phone rings then the PC must answer it. If the PC dials the clock, then it's the clock that requires the dedicated line.

If you have multiple clocks though, and the clocks do the dialing, then you only require 1 dedicated line (the line going in to the PC). Any number of clocks can dial into the PC using that line (although obviously only one can be connected at a time.)

Vote : If the Clock dials, and the PC answers then the solution will probably be cheaper from a line rental point of view.

Phone Line Availability

Because there is a need for a dedicated phone line you may need to consider the possibility of installing such a line at the PC or clock end. As the PC is more likely to be in an "office" environment it's probably easier to have the phone line installed at the PC end. Excess line capacity (via the PABX for example) may already be available.

It should also be noted that if there is an ISDN PABX at one of the ends, then it may be possible to have a dedicated phone number, without necessarily needing a dedicated line. This will however depend on the Telco and PABX capabilities.

Vote : If the Clock dials, and the PC answers then the installation will probably be easier from a line installation point of view.

Portability

The end with the dedicated line should be considered as less portable. The time taken to install a dedicated line means that it is not something which would be considered as highly portable. Therefore if the clocks, or the PC, are likely to me moved on a regular basis then make the non-moving end the dedicated end.

Vote : Either way depending on which end does not require portability.

Flexibility

If the PC dials the clock, then the PC operators have complete flexibility over configuring, updating and collecting from the clock. Apart from the automatic connect times they have the power to connect on demand and make whatever changes they feel are necessary.

If the clock dials the PC then the configuration changes etc are stored on the PC until the next time the clock connects. The clocks will connect according to the schedule you've set, and they can also connect on-demand if a "Dial Now" card is swiped on the clock.

Vote : Setting the PC to dial will allow the operator more immediacy, however as long as the site can be asked to connect this is not a major issue.