Specifications

3000 series eurocard switchers.ib.rev21.doc Page 26 of 36 16/10/2007
External BCD encoding:
The switching logic for the 3000 series is a binary sequence as explained under Switching Logic. Where wire per
crosspoint style operation is required, the following simple method may be used to externally encode wire per
crosspoint signals into the BCD format required by the switcher input.
Note that with this method, the Unlatch In signal is always present and therefore the switcher will not latch to
momentary contact closures. The switches or relays must hold the contact as long as that crosspoint is required.
When no input is crosspoint is selected crosspoint 1 will be active and so any delay between releasing one
crosspoint and activating another will result in the switcher attempting to switch to input 1.
This will have varying effects according to the type of switcher and so caution is advised.
Analogue video. Because switching normally takes place only in sync with the vertical interval, the last
crosspoint activated before the switching point will be the one chosen. Thus for example; a delay of 1 ms between
selections will result in a 95% probability of correct switching and a 5% probability of one field of input 1 being
switched between the two selections.
Other types. Switching is under the control of an oscillator with pulses approximately every 25 ms. Thus
the probability for a 1 ms delay would be 96% for correct switching and 4% for a 25 ms “bite” of the signal on input
1 being inserted.
For audio signals, this would be heard as a “click”.
For digital video signals the result would be a “flash” and
For RS422 signals the result will be determined by the type of equipment connected and could result in almost any
effect ranging from none to catastrophic. Particular care should therefore be exercised with these signals.
Data 0
Crosspoint 1
Crosspoint 2
Crosspoint 3
Crosspoint 4
Crosspoint 5
Data 1
Data 2
No connection
required.
Gnd
+12 Vdc
Regulator IC
Type
78L05
Unlatch in
+5 Vdc
PL 4
Pin
1A
5B
1B
4A
3B
3A
All diodes type 1N4148 or equivalent.