M124 · RTO-144 Connections

M124 - Preamplifier · series S400-LINE · 15 contacts, single row

Rear connector

REAR VIEW · CARD EDGE · 15 CONTACTS1INPUT 150 Ω + / INPUT 372STRAP 2-33STRAP 3-64INPUT 600 Ω + / INPUT 155INPUT 600 Ω −6STRAP 3-67INPUT SHIELD8910GAIN SET RESISTOR11GAIN SET RESISTOR12GND13OUTPUT +14OUTPUT −15VCC-AUDIO +48VInputOutputPowerGround / chassisJumper

Inputs and outputs

M124M124 - PreamplifierINPUT 600 ΩA1 4 / 5INPUT 150 ΩA2 1 / 4INPUT 37.5 ΩA3 1 / 4OUTPUTB1 13 / 14INPUTSOUTPUTSVCC-AUDIO48 V 15 / GND 12⌒ STRAP 3-6 3↔6⌒ STRAP 2-3 2↔3⌒ STRAP 1-2 1↔2⌒ STRAP 3-4 3↔4

Audio connections · RTO-144 A / B

PortSignalDirPin +Pin −Note
A1INPUT 600 Ωin45strap 3-6; transformer phase reversal: pin 4 is high, pin 5 low
A2INPUT 150 Ωin14strap 2-3
A3INPUT 37.5 Ωin14straps 1-2 and 3-4
B1OUTPUTout1314—

Power · bench PSU

RailStyleVoltsMax ASupplyGroundLink
VCC-AUDIO—48—1512—

Jumpers

FunctionDesignationFromTo
600 Ω inputSTRAP 3-636
150 Ω inputSTRAP 2-323
37.5 Ω inputSTRAP 1-212
37.5 Ω inputSTRAP 3-434

Other pins

SignalPins
INPUT SHIELD7
GAIN SET RESISTOR10, 11
COM12

Source: Ward-Beck drawing 124-09-001 iss. 1 (Aug 1968), M124 connector wiring. Verify against the module before wiring.

WBS Ward-Beck Systems Ltd.
Title
M124 RTO-144 connections
Drn.
make_rto144.py
Date
Oct 22 2026