JUNE 2001 – REVISED FEBRUARY 2005

Specifications are subject to change without notice.

Customers should verify actual device performance in their specific applications.

TISP4xxxH3/M3BJ Series for LCAS Protection

APPLICATIONS INFORMATION

Introduction

These protector pairs have been designed to limit the peak voltages on the line terminals of ‘7581/7582/7583 LCAS (Line Card Access Switch)

parts. An LCAS may also be referred to as a Solid-State Relay, SSR, i.e. a replacement of the conventional electro-mechanical relay.

The ‘7581 LCAS has two solid-state switches which connect the telephone line to the line card SLIC (Subscriber Line Interface Circuit), Figure

12, SW1 and SW2. A further two solid-state switches connect the telephone ringing generator to the line, Figure 12, SW3 and SW4. Applied

5-volt logic signals control the condition of the switches to perform the functions of line disconnect, connection to the SLIC and application of

ringing. If excessive long-term overdissipation occurs, a thermal sensor activates thermal shutdown and opens the switches. The SLIC side of

parts.

Figure 12. Basic LCAS Arrangement

RING

RELAY

SLIC

RELAY

RING

GENERATOR

SW5b

SW5a

R1

R2

V

BAT

V

RING

Th1

Th2

Th3

Th4

SLIC

V

bat

TISP4125M3

OR

TISP4125H3

RING

TIP

SW3

SW4

SW1

SW2

LCAS

TISP4219M3

OR

TISP4219H3

AI4XAQ

Additional functions are provided by the ‘7582 (line test access) and the ‘7583 (test-in and test-out access). Up to three conventional electro-

mechanical relays may be replaced by the LCAS. The resulting size reduction can double the line density of a line card.

provide these requirements. The LCAS ’7582 and ’7583 are also covered as the additional switches used in these parts are similar to the

’7581.