Technical data

Installation & Operation Manual GM-TTT

Page 78

7.4 Reference Time Input via External LTC

7.4.1 General

This function requires a special firmware and a hardware module (option L). When displaying

the equipment status (after power-on or pressing the enter button with deactivated menu), the

presence of this special feature will be indicated during the second step of the status

messages: digit 5 shows a “3”.

Basically this special feature is only a different way of a reference time input. Instead of a 1

PPS signal and time/date via a serial interface the external LTC - connected at LTC IN - serves

as the reference time.

All the settings at sub-menus REFERENCE and ZONE are valid as usual. The settings at sub-

menu LTC IN have no effect on the reference time. Programming an offset between the

reference time and the internal clock is done at sub-menu ZONE, not at sub-menu LTC IN.

During main operating mode = time, the LTC output of GM-TTT will be frame accurate to the

external LTC if the LTC of GM-TTT is locked to the external LTC (genlock = LTC) or if both

LTCs are locked to the same source (e.g. to the same black-burst).

7.4.2 Accepting Time, Date and Status Information of the External LTC

GM-TTT accepts the reference time from the LTC input after the LTC has passed three tests:

‘forward’ direction must be detected, it must contain a valid time and the time addresses of

two consecutive frames must be in ascending and continuous order.

The binary groups of the LTC input may carry the date and status information. To select the

right format of these data the sub-menu REFER - MODE 1 has been extended by the field RT-

LTC (digit 4):

Digit 8

Digit 7 Digit 6 Digit 5

Digit 4

Digit 3 Digit 2

Digit 1

RT-LT

RT-LTC Description

0, 1 The LTC input does not carry date and status information.

The date will be the date of the internal clock of GM-TTT.

There is no status available from the LTC input, so the status is set to:

• time zone = UTC,

• “lock” status = free-run,

• antenna signal = received,

• no announcements (Daylight Saving Times changes or Leap Second).