1.01 The WILTRON Model 9041 Transmission Level and Return Loss Measuring Set (see Figure 1-1) fulfills or exceeds the requirements of Western Electric Specification KS 20501 for Through and Terminal Balance of all classes of telephone offices. The Model 9041 incorporates in one instrument the means to measure transmission level, receive frequency response, echo return loss and singing return loss on 4-wire or 2-wire, 600 ohm or 900 ohm circuits. These features permit measurements of loss and balance that meet Bell System, USITA and CCITT specifications, (&) Measuring Features The Model 9041 Measuring Set pro’-vides transmission level measurements from +12dBm to ~48dBm on both 600 and 900 ohm incoming and outgoing trunks over a bandpass of 200Hz to 5kHz. Echo return loss (ERL) and singing return loss (SRL) (high and low) measurements from -lOdB (10dB return gain) to 50dB are provided, Trans-hybrid loss correction of up to 30.8dB in 0.2dB steps is provided for 4-wire return loss measurements* Unused trans-hybrid correction ranges may also be used to correct +7 or -16dB point levels at VFFB's (voice frequency patching bays) or to extend return loss range beyond 50dB on 4-wire circuits. The meter scale and panel controls are marked in red for level measurements and black for return loss measurements. 1.03 The Model 9041 measuring set provides on/off hook reverse battery loop supervision control and supervision indicator lamps for both incoming and outgoing trunk circuits. Decade network buildout (NBO) and drop buildout (DBO) capacitors are provided in the case lid. With these capacitors, the set alone may closely simulate the Office Balance Test Hybrid circuit (Code 970) in 2~wire offices. Tests and several years of use in many offices indicate that this simulation is acceptable for practical circuit order Terminal Balance tests in offices meeting cross office resistance requirements. 1.04 A capacitive ac short circuit is available in the case lid of the Model 9041. This enables holding a working trunk being tested and at the same time checking or measuring short circuit transhybrid loss on the set or the external trunk hybrid without inadvertently causing release of the trunk. The case lid is detachable to allow its use as a precision decade capacitor and ac short during DBO and NBO adjustments, Through Balance measurements and office balancing operations.