Multitech BL-Series Specifications download pdf (Page 122)

Testing a Sign

Sign Testing

It is sometimes necessary to verify the correct operation of a Sign under the control of SIESPACE. It may be

that we need to know that an infrequently used rotating prism is not stuck, or a particular character in a VMS

is functioning.

Modern VMS signs using the SIEMENS UVMS protocol contain comprehensive internal testing and

verification procedures that check communications to each character of the sign, and that the message

being displayed is indeed what was requested. Even the relatively simple rotating prism signs use a reply bit

pattern to verify the position of the prism - this reply is sent back to SIESPACE for checking against the

requested pattern.

Rotating Prism Signs

The only practical test of a rotating prism sign is to alter its setting and verify the returned reply bit pattern.

This can be done manually by setting the sign to a different prism to that on display and verifying that

SIESPACE does not report an "Invalid Legend Returned" fault which would indicate failure of the prism to

rotate.

It is common practice to insert commands into the scheduler to change the setting of rotating prism signs

during the early hours to cause them to rotate, and hence not stick. An override to an abnormal message

(such as FULL), followed by a cancellation of the override is normally used.

VMS Signs

The ability of a VMS sign to be tested depends on the facilities that it provides. Signs complying with the

SIEMENS UVMS protocol provide return status to SIESPACE indicating error conditions on the sign, and

that the requested message has been set. It is also possible to use a special character in the message

which causes all pixel elements of the character to be illuminated (the configuration of this facility should be

verified with the helpdesk).

Typically if a sign is suspect it is recommended that an engineer be dispatched to the sign in order to

observe its behaviour, and the SIESPACE instation be used to override the sign, or a laptop with VMS

diagnostic software used to modify the sign locally.

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Multitech BL-Series Specifications Page 122